RIC7 (ROP-interactive CRIB motif-containing protein 7; locus At4g28560; UniProt F4JLB7) is a member of the 11-protein RIC family in Arabidopsis thaliana. RIC proteins are plant-specific effectors of ROP (Rho of Plants) GTPases, defined by a conserved CRIB (Cdc42/Rac-interactive binding) domain that mediates preferential binding to the GTP-bound (active) form of ROP proteins. RIC7 also contains leucine-rich repeat (LRR) domains, placing it in the receptor-like protein (RLP) family. RIC7 functions as a signaling adaptor downstream of ROP2, negatively regulating both light-induced stomatal opening and ABA-induced stomatal closure in guard cells. Upon light-stimulated ROP2 activation, RIC7 translocates from the nucleus to the plasma membrane, where it directly binds and inhibits the exocyst subunit Exo70B1, thereby restraining vesicle trafficking required for rapid stomatal aperture changes. The ROP2-RIC7-Exo70B1 signaling module provides a brake mechanism that fine-tunes stomatal kinetics to balance CO2 uptake against water loss. RIC7 is highly expressed in guard cells and has also been implicated in pollen tube growth through its interaction with ROP GTPases.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
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GO:0005886
plasma membrane
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: RIC7 dynamically localizes to the plasma membrane region in guard cells upon light stimulation or co-expression with constitutively active ROP2 (Hong et al. 2016). The IBA annotation from phylogenetic inference is consistent with the experimentally demonstrated plasma membrane localization in guard cells.
Reason: Plasma membrane localization of RIC7 is well supported by confocal microscopy of fluorescently tagged RIC7 in Vicia faba guard cells, showing light-dependent and ROP2-activity-dependent relocalization to the plasma membrane. The phylogenetic inference is consistent with experimental data.
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|
GO:0038023
signaling receptor activity
|
IBA
GO_REF:0000033 |
MARK AS OVER ANNOTATED |
Summary: RIC7 is not a signaling receptor per se. It is an intracellular signaling adaptor/effector that binds activated ROP GTPases via its CRIB domain and transduces their signals to downstream targets. While it contains LRR domains typical of receptor-like proteins, there is no evidence that RIC7 itself perceives extracellular ligands or has signaling receptor activity. The IBA annotation likely propagated from receptor-like protein family members that do have receptor activity, but RIC7 lacks a kinase domain and functions as a cytoplasmic effector rather than a receptor.
Reason: The phylogenetic annotation appears to have propagated receptor activity from LRR receptor-like kinase or receptor-like protein family members. However, RIC7 is functionally characterized as an intracellular ROP GTPase effector, not a signaling receptor. Its CRIB motif mediates intracellular protein-protein interactions with activated ROP2, not extracellular ligand perception. Small GTPase binding (GO:0031267) would be more appropriate for this protein.
|
|
GO:0016020
membrane
|
IEA
GO_REF:0000044 |
KEEP AS NON CORE |
Summary: UniProt computationally predicts F4JLB7 as a single-pass type I membrane protein based on ARBA analysis. The protein does contain a predicted signal peptide and transmembrane domain. Experimental evidence supports plasma membrane localization in guard cells, so the general membrane annotation is consistent but less informative than the more specific plasma membrane annotation.
Reason: The annotation is correct but overly broad. The protein localizes to the plasma membrane specifically, and more specific annotations exist (GO:0005886, GO:0016324). This IEA annotation is subsumed by those.
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GO:0016020
membrane
|
TAS
PMID:12068095 Prediction of glycosylphosphatidylinositol-anchored proteins... |
KEEP AS NON CORE |
Summary: PMID:12068095 (Borner et al. 2002) is a genomic analysis predicting GPI-anchored proteins in Arabidopsis. The paper identified RIC7 (At4g28560) as a predicted plasma membrane receptor-like protein. The membrane localization is consistent with this computational prediction and with subsequent experimental evidence.
Reason: The annotation is broadly correct but nonspecific. More informative localization terms (plasma membrane, apical plasma membrane) are available from other annotations. The TAS evidence is based on computational predictions of GPI-anchoring and membrane association rather than direct experimental demonstration.
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GO:0016020
membrane
|
TAS
PMID:12805588 Identification of glycosylphosphatidylinositol-anchored prot... |
KEEP AS NON CORE |
Summary: PMID:12805588 (Borner et al. 2003) is a proteomic and genomic analysis of GPI-anchored proteins in Arabidopsis that identified receptor-like proteins including those at the At4g28560 locus. The membrane annotation is consistent with these findings.
Reason: Same rationale as the other membrane annotations. The annotation is correct but subsumed by more specific plasma membrane and apical plasma membrane annotations from direct experimental evidence.
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|
GO:0009507
chloroplast
|
ISM
GO_REF:0000122 |
MARK AS OVER ANNOTATED |
Summary: The chloroplast localization is based on AtSubP computational prediction (ISM evidence). There is no experimental evidence supporting chloroplast localization for RIC7. Experimental studies show RIC7 localizes to the nucleus in dark conditions and translocates to the plasma membrane upon light stimulation or ROP2 activation (Hong et al. 2016). The protein has a predicted signal peptide and transmembrane domain consistent with secretory pathway/membrane targeting rather than chloroplast import.
Reason: The computational prediction of chloroplast localization is not supported by any experimental evidence. Direct confocal microscopy shows nuclear and plasma membrane localization in guard cells, with no indication of chloroplast targeting. The predicted signal peptide is more consistent with ER/plasma membrane trafficking than chloroplast import.
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GO:0005515
protein binding
|
IPI
PMID:11752391 A genome-wide analysis of Arabidopsis Rop-interactive CRIB m... |
MODIFY |
Summary: PMID:11752391 (Wu et al. 2001) identified RIC7 as one of 11 RIC proteins that interact with Rop GTPases via their CRIB motif, using yeast two-hybrid screening. The with/from column indicates AT3G51300 (ROP3/ARAC1). The protein binding annotation captures this ROP GTPase interaction but is uninformative about the specific nature of the interaction.
Reason: Protein binding (GO:0005515) is too generic per GO curation guidelines. RIC7 specifically binds activated ROP GTPases through its CRIB domain. A more informative annotation would be small GTPase binding (GO:0031267), which accurately describes the ROP GTPase interaction demonstrated by yeast two-hybrid assays and confirmed by subsequent studies.
Proposed replacements:
small GTPase binding
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|
GO:0009860
pollen tube growth
|
IMP
PMID:11752391 A genome-wide analysis of Arabidopsis Rop-interactive CRIB m... |
KEEP AS NON CORE |
Summary: Wu et al. (2001) showed that overexpression of RIC7 in tobacco pollen tubes causes growth inhibition, demonstrating a role in pollen tube growth. The IMP evidence is appropriate for this overexpression phenotype. While later studies (Hong et al. 2016) established RIC7's primary biological role in guard cell stomatal regulation, the pollen tube growth involvement is experimentally supported.
Reason: The annotation is experimentally supported by pollen tube overexpression assays, but the primary characterized biological role of RIC7 is in guard cell stomatal regulation, not pollen tube growth. The pollen tube phenotype may reflect a secondary or overexpression-specific effect. The qualifier acts_upstream_of_or_within appropriately conveys uncertainty about the directness of involvement.
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|
GO:0016324
apical plasma membrane
|
IDA
PMID:11752391 A genome-wide analysis of Arabidopsis Rop-interactive CRIB m... |
ACCEPT |
Summary: Wu et al. (2001) showed localization of RIC proteins including RIC7 in pollen tubes. The IDA evidence indicates direct observation of RIC7 at the apical plasma membrane region. This is consistent with later findings (Hong et al. 2016) showing RIC7 plasma membrane localization in guard cells upon ROP activation. In pollen tubes, the apical region is where ROP GTPases are concentrated and active.
Reason: The apical plasma membrane localization in pollen tubes is supported by IDA evidence from the original characterization study. This is consistent with RIC7's role as a ROP effector, since ROP GTPases are enriched at the pollen tube apex.
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|
GO:0007165
signal transduction
|
IC
PMID:11751054 The leucine-rich repeat as a protein recognition motif. |
KEEP AS NON CORE |
Summary: The signal transduction annotation is inferred by curator (IC) based on protein binding evidence (with/from GO:0005515) and supported by a review on LRR protein recognition motifs (PMID:11751054, Kobe & Kajava 2001). The inference that an LRR-containing protein that binds ROP GTPases participates in signal transduction is biologically sound. RIC7 is indeed a signaling adaptor in the ROP2-RIC7-Exo70B1 pathway.
Reason: Signal transduction is correct but very broad. RIC7 specifically participates in ROP GTPase signaling that regulates stomatal movement. The annotation is not wrong but does not capture the specific signaling pathway. The IC evidence and general review reference are appropriate for this level of annotation.
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The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
RIC7 (gene locus At4g28560, UniProt accession F4JLB7) encodes a ROP-interactive CRIB motif-containing protein 7 in Arabidopsis thaliana (hong2016therop2ric7pathway pages 1-2). This protein belongs to the RIC family, a group of eleven structurally divergent proteins in Arabidopsis that function as downstream effectors of ROP (Rho of Plants) GTPases (feiguelman2018ropgtpasesstructurefunction pages 1-5). The identity of RIC7 has been confirmed through molecular studies showing it contains the characteristic CRIB (Cdc42/Rac-interactive binding) domain that mediates interaction with activated ROP proteins (hong2016therop2ric7pathway pages 1-2, feiguelman2018ropgtpasesstructurefunction pages 10-13).
RIC proteins represent a plant-specific family of ROP effectors characterized by the presence of a CRIB domain (feiguelman2018ropgtpasesstructurefunction pages 10-13, smokvarska2021functionofmembrane pages 1-2). The CRIB domain is a conserved sequence motif found in effector proteins that interact with GTP-bound forms of Rho-family GTPases (smokvarska2021functionofmembrane pages 1-2). In plants, CRIB domains are found not only in RIC proteins but also in certain ROPGAPs (ROP GTPase-activating proteins), where they enhance binding between ROPs and ROPGAPs and are required for subcellular localization (feiguelman2018ropgtpasesstructurefunction pages 10-13).
Arabidopsis possesses eleven RIC proteins (RIC1-11) that have evolved to control various ROP GTPase-dependent pathways through functional diversification (hong2016therop2ric7pathway pages 1-2). While some RIC family members like RIC1, RIC3, and RIC4 regulate cytoskeletal organization during processes such as pollen tube growth and cell morphogenesis (feiguelman2018ropgtpasesstructurefunction pages 1-5), RIC7 represents a specialized branch involved in guard cell signaling rather than the cytoskeletal functions typical of other RIC proteins (feiguelman2018ropgtpasesstructurefunction pages 1-5).
The defining feature of RIC7 is its CRIB motif, which enables direct interaction with activated (GTP-bound) ROP proteins (hong2016therop2ric7pathway pages 1-2, feiguelman2018ropgtpasesstructurefunction pages 10-13). This domain is essential for RIC7 to function as a molecular effector that transduces ROP signaling to downstream cellular processes. The CRIB domain binds preferentially to the active conformation of ROPs, ensuring signal specificity (smokvarska2021functionofmembrane pages 1-2).
The primary function of RIC7 is to negatively regulate stomatal movements in Arabidopsis guard cells (hong2016therop2ric7pathway pages 1-2, hong2016therop2ric7pathway pages 3-4). Genetic and biochemical studies have established RIC7 as a key component that fine-tunes both light-induced stomatal opening and abscisic acid (ABA)-induced stomatal closure.
Knockout studies using the ric7-1 mutant (which harbors a T-DNA insertion in the second intron) demonstrated that loss of RIC7 function leads to accelerated light-induced stomatal opening (hong2016therop2ric7pathway pages 3-4). After 1-2 hours of light irradiation, ric7-1 mutant stomata opened approximately 18% more widely than wild-type stomata (hong2016therop2ric7pathway pages 3-4). Conversely, plants overexpressing RIC7 under the control of the 35S promoter exhibited slower light-induced stomatal opening compared to wild-type plants (hong2016therop2ric7pathway pages 3-4). Complementation lines expressing genomic RIC7 driven by its native promoter in the ric7-1 background restored wild-type stomatal opening kinetics, confirming that the rapid opening phenotype was due to RIC7 loss of function (hong2016therop2ric7pathway pages 3-4).
RIC7 also suppresses ABA-induced stomatal closure. The ric7-1 knockout mutant exhibited faster ABA-induced stomatal closure than wild-type, with differences evident as early as 30 minutes after ABA treatment (hong2016therop2ric7pathway pages 3-4). RIC7 overexpression lines showed slower ABA-induced closure (hong2016therop2ric7pathway pages 3-4). These results indicate that RIC7 functions as a negative regulator of both stomatal opening and closure, similar to its upstream regulator ROP2 (hong2016therop2ric7pathway pages 8-9).
RIC7 does not function as a substrate-specific enzyme or transporter. Instead, it operates as a signaling adaptor protein that links ROP2 GTPase activity to the vesicle trafficking machinery required for stomatal movement (hong2016therop2ric7pathway pages 8-9, hong2016therop2ric7pathway pages 9-10).
Interaction with ROP2: RIC7 functions downstream of ROP2, a plant Rho-type GTPase that negatively regulates stomatal movements (hong2016therop2ric7pathway pages 1-2, hong2016therop2ric7pathway pages 8-9). Previous work established that RIC7 binds to activated ROP2 in vitro, positioning it as a ROP2 effector (hong2016therop2ric7pathway pages 1-2). The interaction between RIC7 and active ROP2 is mediated by the CRIB domain (hong2016therop2ric7pathway pages 1-2).
Direct Binding to Exo70B1: A critical discovery was the identification of Exo70B1 (exocyst subunit Exo70 family protein B1) as a direct interaction partner of RIC7 (hong2016therop2ric7pathway pages 4-5). Multiple experimental approaches confirmed this interaction:
Importantly, BiFC assays revealed that Exo70B1 does not bind directly to ROP2 (hong2016therop2ric7pathway pages 4-5), indicating that RIC7 serves as a linker protein connecting ROP2 to the exocyst machinery. This differs from yeast and animal systems where Rho GTPases often bind directly to Exo70 proteins (hong2016therop2ric7pathway pages 8-9). The requirement for a linker protein may reflect the absence of conserved C-terminal Rho-binding motifs in plant Exo70 proteins (hong2016therop2ric7pathway pages 8-9).
Functional Relationship with Exo70B1: RIC7 and Exo70B1 have opposing functions in stomatal regulation. While RIC7 is a negative regulator of light-induced stomatal opening, Exo70B1 is a positive regulator (hong2016therop2ric7pathway pages 5-7, hong2016therop2ric7pathway pages 9-10). The exo70b1-1 and exo70b1-2 knockout mutants showed retarded light-induced stomatal opening, with stomata opening approximately 14% less than wild-type after 1 hour of light (hong2016therop2ric7pathway pages 5-7). Genetic epistasis analysis using the ric7-1/exo70b1-1 double knockout mutant demonstrated that the double mutant phenotype resembled exo70b1-1 rather than ric7-1, indicating that Exo70B1 functions downstream of RIC7 (hong2016therop2ric7pathway pages 7-8).
The proposed mechanism is that RIC7 binding inhibits Exo70B1 function, thereby restraining vesicle trafficking and limiting the rate of stomatal opening (hong2016therop2ric7pathway pages 9-10). This creates a brake mechanism that prevents excessive stomatal opening and associated water loss while still allowing efficient COโ uptake for photosynthesis (hong2016therop2ric7pathway pages 8-9, hong2016therop2ric7pathway pages 9-10).
RIC7 exhibits stimulus-dependent subcellular localization, which is critical for its regulatory function (hong2016therop2ric7pathway pages 7-8, hong2016therop2ric7pathway pages 5-7).
Localization Under Dark Conditions: In guard cells maintained in darkness, CFP-tagged RIC7 localizes predominantly to the nucleus (hong2016therop2ric7pathway pages 7-8, hong2016therop2ric7pathway pages 5-7). Under these conditions, YFP-tagged Exo70B1 shows a punctate pattern in the cytosol and nucleus (hong2016therop2ric7pathway pages 7-8).
Light-Induced Relocalization: Upon light irradiation (2 hours of white light), a subset of RIC7 relocates from the nucleus to the plasma membrane region, where it co-localizes with Exo70B1 (hong2016therop2ric7pathway pages 7-8, hong2016therop2ric7pathway pages 5-7). Fluorescence intensity profiles confirmed co-localization of YFP-Exo70B1 and CFP-RIC7 at the plasma membrane in light-treated guard cells (hong2016therop2ric7pathway pages 7-8).
ROP2 Activity-Dependent Localization: The relocalization of RIC7 to the plasma membrane is dependent on ROP2 activity. When co-expressed with constitutively active ROP2 (CA-ROP2), RIC7 and Exo70B1 both localize to the plasma membrane region even in the absence of light (hong2016therop2ric7pathway pages 7-8). In contrast, when co-expressed with a dominant-negative ROP2 (DN-ROP2), RIC7 remains primarily nuclear and Exo70B1 maintains its punctate cytoplasmic/nuclear distribution without plasma membrane enrichment (hong2016therop2ric7pathway pages 7-8). These findings indicate that light-mediated ROP2 activation triggers the recruitment of both RIC7 and Exo70B1 to the plasma membrane, where RIC7 can then modulate Exo70B1 function (hong2016therop2ric7pathway pages 7-8, hong2016therop2ric7pathway pages 9-10).
RIC7 is highly expressed in stomatal guard cells, as demonstrated by RIC7 promoter::ฮฒ-glucuronidase reporter analysis (hong2016therop2ric7pathway pages 3-4). Guard cells regulate stomatal apertures to balance COโ uptake for photosynthesis against water loss through transpiration. Stomatal opening requires increases in guard cell volume driven by ion accumulation and water influx, necessitating expansion of the plasma membrane and reorganization of the vacuolar membrane (hong2016therop2ric7pathway pages 9-10).
ROP2 (also known as RAC2) is a member of the plant-specific ROP subfamily of Rho GTPases and functions as a negative regulator of stomatal movements (hong2016therop2ric7pathway pages 1-2, feiguelman2018ropgtpasesstructurefunction pages 1-5). Like all small GTPases, ROP proteins cycle between an inactive GDP-bound state and an active GTP-bound state. This cycle is regulated by guanine nucleotide exchange factors (GEFs) that promote GDP release and GTP binding, and GTPase-activating proteins (GAPs) that enhance GTP hydrolysis (feiguelman2018ropgtpasesstructurefunction pages 1-5, smokvarska2021functionofmembrane pages 1-2).
In the context of stomatal regulation, light perception by phototropins and chlorophylls activates signaling pathways that ultimately modulate ROP2 activity (hong2016therop2ric7pathway pages 9-10). The current model proposes that light-induced stomatal opening activates positive regulatory pathways but simultaneously engages negative regulatory mechanisms, including the ROP2-RIC7-Exo70B1 pathway, to prevent excessive opening (hong2016therop2ric7pathway pages 8-9, hong2016therop2ric7pathway pages 9-10).
The functional interaction between RIC7 and Exo70B1 implicates vesicle trafficking as a critical regulatory target in stomatal movement (hong2016therop2ric7pathway pages 9-10). Exo70B1 is a component of the exocyst complex, an eight-subunit complex (Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70, and Exo84) that mediates tethering and spatial targeting of post-Golgi vesicles to the plasma membrane prior to fusion (hong2016therop2ric7pathway pages 1-2, hong2016therop2ric7pathway pages 2-3).
In guard cells, Exo70B1 co-localizes with Exo84B, another exocyst component, supporting its role in exocyst function (hong2016therop2ric7pathway pages 7-8). However, Exo70B1 shows minimal co-localization with Golgi or trans-Golgi network/early endosome (TGN/EE) markers (only 3-4% overlap with Golgi marker ST-GFP and 11-12% with TGN/EE marker YFP-SYP61), suggesting involvement in non-conventional trafficking pathways or exocyst-positive organelle (EXPO)-mediated exocytosis (hong2016therop2ric7pathway pages 8-9).
The proposed mechanism is that Exo70B1 facilitates the trafficking of ion transporters and membrane materials to the plasma membrane and vacuolar membrane during stomatal opening (hong2016therop2ric7pathway pages 9-10). RIC7 binding to Exo70B1 inhibits this trafficking function, thereby limiting the rate of membrane expansion and ion transporter delivery, which in turn restrains the rate of stomatal opening (hong2016therop2ric7pathway pages 9-10). This provides a mechanism for plants to fine-tune stomatal aperture in response to environmental conditions.
RIC7 also modulates ABA-induced stomatal closure, although the precise mechanism differs from its role in light-induced opening (hong2016therop2ric7pathway pages 3-4, hong2016therop2ric7pathway pages 8-9). The observation that ric7 mutants exhibit faster ABA-induced closure suggests that RIC7 normally acts to dampen or slow the closure response (hong2016therop2ric7pathway pages 3-4). This may reflect a general role for RIC7 in modulating the kinetics of membrane trafficking events during stomatal movements, regardless of the directional stimulus.
Previous work has established that ROP proteins and ABA signaling form negative feedback loops (feiguelman2018ropgtpasesstructurefunction pages 1-5). ABA signaling suppresses ROP activation by promoting degradation of ROPGEFs, while ROP signaling suppresses ABA responses by physical interactions between ROPs (particularly ROP10 and ROP11) and ABI1/ABI2 PP2C phosphatases, negative regulators of ABA signaling (feiguelman2018ropgtpasesstructurefunction pages 1-5). RIC7's role in this network likely involves transducing ROP2 signals that modulate the kinetics of stomatal responses to both positive (light) and negative (ABA) stimuli.
The characterization of RIC7 is supported by multiple lines of experimental evidence employing diverse methodologies:
Genetic Evidence:
- T-DNA insertion mutant ric7-1 (GK_062G02) with insertion in the second intron (hong2016therop2ric7pathway pages 1-2, hong2016therop2ric7pathway pages 3-4)
- RIC7 overexpression lines (OX1, OX3, OX8) under 35S promoter control (hong2016therop2ric7pathway pages 3-4)
- Complementation lines expressing genomic RIC7 under native promoter in ric7-1 background (hong2016therop2ric7pathway pages 3-4)
- Double mutant ric7-1/exo70b1-1 for epistasis analysis (hong2016therop2ric7pathway pages 7-8)
Biochemical Evidence:
- Yeast two-hybrid screens identifying Exo70B1 as RIC7-interacting protein (hong2016therop2ric7pathway pages 4-5)
- In vitro GST pull-down assays demonstrating direct RIC7-Exo70B1 interaction (hong2016therop2ric7pathway pages 4-5)
- Quantitative RT-PCR confirming gene expression levels in mutants and transgenics (hong2016therop2ric7pathway pages 2-3)
Cell Biological Evidence:
- Bimolecular fluorescence complementation (BiFC) assays in Nicotiana benthamiana confirming RIC7-Exo70B1 interaction in vivo (hong2016therop2ric7pathway pages 4-5)
- Transient expression of fluorescently tagged proteins in Vicia faba guard cells via particle bombardment (hong2016therop2ric7pathway pages 2-3, hong2016therop2ric7pathway pages 7-8)
- Confocal microscopy analysis of subcellular localization under different conditions (dark, light, with CA-ROP2, with DN-ROP2) (hong2016therop2ric7pathway pages 7-8, hong2016therop2ric7pathway pages 5-7)
- Co-localization studies with organelle markers (hong2016therop2ric7pathway pages 8-9)
Physiological Evidence:
- Stomatal aperture measurements showing altered light-induced opening kinetics in ric7 mutants and overexpression lines (hong2016therop2ric7pathway pages 3-4)
- ABA-induced stomatal closure assays demonstrating RIC7's role in closure kinetics (hong2016therop2ric7pathway pages 3-4)
- Promoter::ฮฒ-glucuronidase reporter analysis revealing RIC7 expression patterns (hong2016therop2ric7pathway pages 3-4)
The RIC family exhibits functional diversification, with different members regulating distinct cellular processes (feiguelman2018ropgtpasesstructurefunction pages 1-5). While RIC7 is specialized for guard cell signaling and vesicle trafficking regulation, other RIC proteins have well-characterized roles in cytoskeletal regulation:
This functional diversity reflects the evolution of the RIC family to mediate different downstream outputs of ROP signaling in different cellular contexts, despite sharing the common CRIB domain that enables ROP interaction (feiguelman2018ropgtpasesstructurefunction pages 1-5).
The characterization of RIC7 published by Hong et al. in 2016 remains the most comprehensive functional study of this protein (hong2016therop2ric7pathway pages 1-2). Recent reviews (2020-2022) on ROP signaling pathways provide broader context for understanding RIC proteins as ROP effectors (feiguelman2018ropgtpasesstructurefunction pages 1-5, smokvarska2021functionofmembrane pages 1-2), but RIC7-specific studies remain limited compared to other RIC family members like RIC1, RIC3, and RIC4.
Key remaining questions include:
1. The precise molecular mechanism by which RIC7 binding inhibits Exo70B1 function
2. Whether RIC7 interacts with other exocyst components or trafficking machinery
3. The structural basis of RIC7-Exo70B1 interaction
4. Potential roles of RIC7 in other cell types beyond guard cells
5. The evolutionary origin and conservation of RIC7 function in other plant species
| Category | Findings for RIC7 (Arabidopsis thaliana) | Evidence / citation |
|---|---|---|
| Gene / protein identity | RIC7; Arabidopsis locus At4g28560; UniProt accession F4JLB7; protein name ROP-interactive CRIB motif-containing protein 7; organism Arabidopsis thaliana. Identity is consistent with the Arabidopsis RIC family described as CRIB-domain ROP effectors. | (hong2016therop2ric7pathway pages 1-2, feiguelman2018ropgtpasesstructurefunction pages 1-5) |
| Family / defining features | RIC7 belongs to the RIC (ROP-interactive CRIB motif-containing) family, a set of structurally divergent Arabidopsis ROP effectors that bind activated ROP GTPases via a CRIB domain. Arabidopsis contains 11 RIC proteins. | (hong2016therop2ric7pathway pages 1-2, feiguelman2018ropgtpasesstructurefunction pages 10-13, smokvarska2021functionofmembrane pages 1-2) |
| Current domain understanding | The defining experimentally supported feature is the CRIB motif/domain, which mediates interaction with active ROPs in plant RIC proteins. More broadly, CRIB-containing proteins function as downstream effectors of Rho/ROP-family GTPases. | (hong2016therop2ric7pathway pages 1-2, feiguelman2018ropgtpasesstructurefunction pages 10-13, smokvarska2021functionofmembrane pages 1-2) |
| Primary molecular function | RIC7 is a negative regulator of stomatal movement, especially light-induced stomatal opening; it also suppresses ABA-induced stomatal closure. Mechanistically, it acts downstream of ROP2 and inhibits the positive stomatal-opening factor Exo70B1, thereby restraining excess opening. | (hong2016therop2ric7pathway pages 1-2, hong2016therop2ric7pathway pages 3-4, hong2016therop2ric7pathway pages 8-9, hong2016therop2ric7pathway pages 9-10) |
| Pathway position | In the best-supported pathway, active ROP2 โ RIC7 โ Exo70B1 inhibition, with RIC7 functioning as a linker/effector that transduces ROP2 signaling to vesicle-trafficking machinery in guard cells. | (hong2016therop2ric7pathway pages 8-9, hong2016therop2ric7pathway pages 9-10) |
| Direct interaction partners | ROP2: prior work placed RIC7 downstream of active ROP2; Exo70B1: directly binds RIC7 in yeast two-hybrid, in vitro pull-down, and BiFC assays. Exo70B1 did not bind ROP2 directly in the reported BiFC assay, supporting a linker role for RIC7. | (hong2016therop2ric7pathway pages 1-2, hong2016therop2ric7pathway pages 4-5, hong2016therop2ric7pathway pages 8-9) |
| Positive / opposing functional partner | Exo70B1 is a positive regulator of light-induced stomatal opening, whereas RIC7 is negative; the exo70b1 phenotype is epistatic to ric7 in double mutants, supporting Exo70B1 as a downstream target of RIC7. | (hong2016therop2ric7pathway pages 5-7, hong2016therop2ric7pathway pages 7-8, hong2016therop2ric7pathway pages 9-10) |
| Subcellular localization | In guard cells under dark conditions, RIC7 is localized mostly to the nucleus; under light or with constitutively active ROP2, a subset of RIC7 relocates to the plasma membrane region, where it co-localizes with Exo70B1. This dynamic relocalization is consistent with stimulus-dependent signaling. | (hong2016therop2ric7pathway pages 7-8, hong2016therop2ric7pathway pages 5-7) |
| Localization context of partner | Exo70B1 localizes to the plasma membrane region, nucleus, and cytosolic puncta; it co-localizes with Exo84B but shows little co-localization with Golgi or TGN/EE markers, suggesting association with exocyst-related / noncanonical trafficking compartments relevant to RIC7 action. | (hong2016therop2ric7pathway pages 7-8, hong2016therop2ric7pathway pages 8-9, hong2016therop2ric7pathway pages 9-10) |
| Tissue / expression context | RIC7 promoter activity is detected broadly in young tissues and is high in stomatal guard cells, supporting a direct role in guard-cell physiology. | (hong2016therop2ric7pathway pages 3-4) |
| Biological processes implicated | Guard-cell signaling, stomatal opening, ABA-responsive stomatal closure, and likely vesicle trafficking / membrane remodeling needed for stomatal movement. The proposed mechanism is inhibition of exocyst-mediated trafficking required for rapid opening. | (hong2016therop2ric7pathway pages 1-2, hong2016therop2ric7pathway pages 9-10) |
| Functional model | Light activates stomatal opening pathways but also a brake mechanism: ROP2 recruits RIC7 and Exo70B1 to the plasma membrane region; RIC7 binds Exo70B1 and inhibits its function, fine-tuning opening kinetics and preventing excessive water loss. | (hong2016therop2ric7pathway pages 7-8, hong2016therop2ric7pathway pages 8-9, hong2016therop2ric7pathway pages 9-10) |
| Genetic evidence | ric7-1 knockout shows faster light-induced opening and faster ABA-induced closure than wild type; RIC7 complementation restores wild-type behavior; RIC7 overexpression slows both responses. | (hong2016therop2ric7pathway pages 3-4) |
| Biochemical / cell-biological evidence | Evidence includes yeast two-hybrid, in vitro GST pull-down, BiFC, transient fluorescent localization in Vicia faba guard cells, and Arabidopsis mutant / complementation / overexpression analysis. Together these support direct RIC7โExo70B1 interaction and dynamic localization. | (hong2016therop2ric7pathway pages 4-5, hong2016therop2ric7pathway pages 5-7, hong2016therop2ric7pathway pages 7-8) |
| Broader family context | RIC proteins are diverse ROP effectors. Other Arabidopsis RICs regulate actin and microtubule organization and polarized growth, indicating that RIC7 likely represents a specialized branch of ROP effector biology tied to guard-cell membrane trafficking rather than the canonical pollen-tube cytoskeletal outputs of RIC1/3/4. | (hong2016therop2ric7pathway pages 1-2, feiguelman2018ropgtpasesstructurefunction pages 1-5, smokvarska2021functionofmembrane pages 1-2) |
| Key references summarized in evidence base | Primary experimental study: Hong et al., 2016, New Phytologist on the ROP2โRIC7โExo70B1 pathway in stomatal opening. Conceptual background from ROP signaling reviews in Plant Physiology 2018 and Plant Physiology 2021. | (hong2016therop2ric7pathway pages 1-2, feiguelman2018ropgtpasesstructurefunction pages 1-5, smokvarska2021functionofmembrane pages 1-2) |
Table: This table compiles the verified identity, molecular function, localization, pathway role, and supporting evidence for Arabidopsis RIC7. It is useful as a concise annotation-ready summary centered on the experimentally supported ROP2-RIC7-Exo70B1 guard-cell signaling module.
RIC7 (At4g28560, UniProt F4JLB7) is a ROP-interactive CRIB motif-containing protein that functions as a negative regulator of stomatal movements in Arabidopsis thaliana. As a member of the eleven-protein RIC family, RIC7 serves as a downstream effector of ROP2 GTPase, transducing signals to the vesicle trafficking machinery through direct interaction with exocyst subunit Exo70B1. RIC7 exhibits dynamic subcellular localization, moving from the nucleus to the plasma membrane region in response to light stimulation or ROP2 activation. By binding to and inhibiting Exo70B1, RIC7 restrains excessive stomatal opening, providing a brake mechanism that balances COโ uptake against water loss. This function has been validated through comprehensive genetic, biochemical, and cell biological approaches, including analysis of knockout mutants, overexpression lines, protein-protein interaction assays, and subcellular localization studies. RIC7 represents a specialized branch of RIC protein evolution, diverging from the cytoskeletal regulatory functions of other family members to perform a unique role in guard cell physiology and gas exchange regulation.
Primary Reference: Hong, D., Jeon, B.W., Kim, S.Y., Hwang, J.-U., & Lee, Y. (2016). The ROP2-RIC7 pathway negatively regulates light-induced stomatal opening by inhibiting exocyst subunit Exo70B1 in Arabidopsis. New Phytologist, 209(2), 624-635. doi:10.1111/nph.13625
Publication Date: October 2015 (published online), January 2016 (print)
DOI/URL: https://doi.org/10.1111/nph.13625
References
(hong2016therop2ric7pathway pages 1-2): Daewoong Hong, Byeong Wook Jeon, Soo Young Kim, JaeโUng Hwang, and Youngsook Lee. The rop2-ric7 pathway negatively regulates light-induced stomatal opening by inhibiting exocyst subunit exo70b1 in arabidopsis. The New phytologist, 209 2:624-35, Oct 2016. URL: https://doi.org/10.1111/nph.13625, doi:10.1111/nph.13625. This article has 72 citations.
(feiguelman2018ropgtpasesstructurefunction pages 1-5): Gil Feiguelman, Ying Fu, and Shaul Yalovsky. Rop gtpases structure-function and signaling pathways1[open]. Plant Physiology, 176:57-79, Nov 2018. URL: https://doi.org/10.1104/pp.17.01415, doi:10.1104/pp.17.01415. This article has 227 citations and is from a highest quality peer-reviewed journal.
(feiguelman2018ropgtpasesstructurefunction pages 10-13): Gil Feiguelman, Ying Fu, and Shaul Yalovsky. Rop gtpases structure-function and signaling pathways1[open]. Plant Physiology, 176:57-79, Nov 2018. URL: https://doi.org/10.1104/pp.17.01415, doi:10.1104/pp.17.01415. This article has 227 citations and is from a highest quality peer-reviewed journal.
(smokvarska2021functionofmembrane pages 1-2): Marija Smokvarska, Yvon Jaillais, and Alexandre Martiniรจre. Function of membrane domains in rho-of-plant signaling. Plant Physiology, 185:663-681, Jan 2021. URL: https://doi.org/10.1093/plphys/kiaa082, doi:10.1093/plphys/kiaa082. This article has 54 citations and is from a highest quality peer-reviewed journal.
(hong2016therop2ric7pathway pages 3-4): Daewoong Hong, Byeong Wook Jeon, Soo Young Kim, JaeโUng Hwang, and Youngsook Lee. The rop2-ric7 pathway negatively regulates light-induced stomatal opening by inhibiting exocyst subunit exo70b1 in arabidopsis. The New phytologist, 209 2:624-35, Oct 2016. URL: https://doi.org/10.1111/nph.13625, doi:10.1111/nph.13625. This article has 72 citations.
(hong2016therop2ric7pathway pages 8-9): Daewoong Hong, Byeong Wook Jeon, Soo Young Kim, JaeโUng Hwang, and Youngsook Lee. The rop2-ric7 pathway negatively regulates light-induced stomatal opening by inhibiting exocyst subunit exo70b1 in arabidopsis. The New phytologist, 209 2:624-35, Oct 2016. URL: https://doi.org/10.1111/nph.13625, doi:10.1111/nph.13625. This article has 72 citations.
(hong2016therop2ric7pathway pages 9-10): Daewoong Hong, Byeong Wook Jeon, Soo Young Kim, JaeโUng Hwang, and Youngsook Lee. The rop2-ric7 pathway negatively regulates light-induced stomatal opening by inhibiting exocyst subunit exo70b1 in arabidopsis. The New phytologist, 209 2:624-35, Oct 2016. URL: https://doi.org/10.1111/nph.13625, doi:10.1111/nph.13625. This article has 72 citations.
(hong2016therop2ric7pathway pages 4-5): Daewoong Hong, Byeong Wook Jeon, Soo Young Kim, JaeโUng Hwang, and Youngsook Lee. The rop2-ric7 pathway negatively regulates light-induced stomatal opening by inhibiting exocyst subunit exo70b1 in arabidopsis. The New phytologist, 209 2:624-35, Oct 2016. URL: https://doi.org/10.1111/nph.13625, doi:10.1111/nph.13625. This article has 72 citations.
(hong2016therop2ric7pathway pages 5-7): Daewoong Hong, Byeong Wook Jeon, Soo Young Kim, JaeโUng Hwang, and Youngsook Lee. The rop2-ric7 pathway negatively regulates light-induced stomatal opening by inhibiting exocyst subunit exo70b1 in arabidopsis. The New phytologist, 209 2:624-35, Oct 2016. URL: https://doi.org/10.1111/nph.13625, doi:10.1111/nph.13625. This article has 72 citations.
(hong2016therop2ric7pathway pages 7-8): Daewoong Hong, Byeong Wook Jeon, Soo Young Kim, JaeโUng Hwang, and Youngsook Lee. The rop2-ric7 pathway negatively regulates light-induced stomatal opening by inhibiting exocyst subunit exo70b1 in arabidopsis. The New phytologist, 209 2:624-35, Oct 2016. URL: https://doi.org/10.1111/nph.13625, doi:10.1111/nph.13625. This article has 72 citations.
(hong2016therop2ric7pathway pages 2-3): Daewoong Hong, Byeong Wook Jeon, Soo Young Kim, JaeโUng Hwang, and Youngsook Lee. The rop2-ric7 pathway negatively regulates light-induced stomatal opening by inhibiting exocyst subunit exo70b1 in arabidopsis. The New phytologist, 209 2:624-35, Oct 2016. URL: https://doi.org/10.1111/nph.13625, doi:10.1111/nph.13625. This article has 72 citations.
(feiguelman2018ropgtpasesstructurefunction pages 20-23): Gil Feiguelman, Ying Fu, and Shaul Yalovsky. Rop gtpases structure-function and signaling pathways1[open]. Plant Physiology, 176:57-79, Nov 2018. URL: https://doi.org/10.1104/pp.17.01415, doi:10.1104/pp.17.01415. This article has 227 citations and is from a highest quality peer-reviewed journal.
id: F4JLB7
gene_symbol: RIC7
product_type: PROTEIN
status: COMPLETE
taxon:
id: NCBITaxon:3702
label: Arabidopsis thaliana
description: >-
RIC7 (ROP-interactive CRIB motif-containing protein 7; locus At4g28560; UniProt
F4JLB7) is a member of the 11-protein RIC family in Arabidopsis thaliana. RIC
proteins are plant-specific effectors of ROP (Rho of Plants) GTPases, defined by
a conserved CRIB (Cdc42/Rac-interactive binding) domain that mediates
preferential binding to the GTP-bound (active) form of ROP proteins. RIC7 also
contains leucine-rich repeat (LRR) domains, placing it in the receptor-like
protein (RLP) family. RIC7 functions as a signaling adaptor downstream of ROP2,
negatively regulating both light-induced stomatal opening and ABA-induced
stomatal closure in guard cells. Upon light-stimulated ROP2 activation, RIC7
translocates from the nucleus to the plasma membrane, where it directly binds
and inhibits the exocyst subunit Exo70B1, thereby restraining vesicle
trafficking required for rapid stomatal aperture changes. The ROP2-RIC7-Exo70B1
signaling module provides a brake mechanism that fine-tunes stomatal kinetics to
balance CO2 uptake against water loss. RIC7 is highly expressed in guard cells
and has also been implicated in pollen tube growth through its interaction with
ROP GTPases.
existing_annotations:
- term:
id: GO:0005886
label: plasma membrane
evidence_type: IBA
original_reference_id: GO_REF:0000033
qualifier: is_active_in
review:
summary: >-
RIC7 dynamically localizes to the plasma membrane region in guard cells upon
light stimulation or co-expression with constitutively active ROP2 (Hong et
al. 2016). The IBA annotation from phylogenetic inference is consistent with
the experimentally demonstrated plasma membrane localization in guard cells.
action: ACCEPT
reason: >-
Plasma membrane localization of RIC7 is well supported by confocal microscopy
of fluorescently tagged RIC7 in Vicia faba guard cells, showing
light-dependent and ROP2-activity-dependent relocalization to the plasma
membrane. The phylogenetic inference is consistent with experimental data.
- term:
id: GO:0038023
label: signaling receptor activity
evidence_type: IBA
original_reference_id: GO_REF:0000033
qualifier: enables
review:
summary: >-
RIC7 is not a signaling receptor per se. It is an intracellular signaling
adaptor/effector that binds activated ROP GTPases via its CRIB domain and
transduces their signals to downstream targets. While it contains LRR domains
typical of receptor-like proteins, there is no evidence that RIC7 itself
perceives extracellular ligands or has signaling receptor activity. The IBA
annotation likely propagated from receptor-like protein family members that do
have receptor activity, but RIC7 lacks a kinase domain and functions as a
cytoplasmic effector rather than a receptor.
action: MARK_AS_OVER_ANNOTATED
reason: >-
The phylogenetic annotation appears to have propagated receptor activity from
LRR receptor-like kinase or receptor-like protein family members. However,
RIC7 is functionally characterized as an intracellular ROP GTPase effector,
not a signaling receptor. Its CRIB motif mediates intracellular
protein-protein interactions with activated ROP2, not extracellular ligand
perception. Small GTPase binding (GO:0031267) would be more appropriate for
this protein.
- term:
id: GO:0016020
label: membrane
evidence_type: IEA
original_reference_id: GO_REF:0000044
qualifier: located_in
review:
summary: >-
UniProt computationally predicts F4JLB7 as a single-pass type I membrane
protein based on ARBA analysis. The protein does contain a predicted signal
peptide and transmembrane domain. Experimental evidence supports plasma
membrane localization in guard cells, so the general membrane annotation is
consistent but less informative than the more specific plasma membrane
annotation.
action: KEEP_AS_NON_CORE
reason: >-
The annotation is correct but overly broad. The protein localizes to the
plasma membrane specifically, and more specific annotations exist
(GO:0005886, GO:0016324). This IEA annotation is subsumed by those.
- term:
id: GO:0016020
label: membrane
evidence_type: TAS
original_reference_id: PMID:12068095
qualifier: located_in
review:
summary: >-
PMID:12068095 (Borner et al. 2002) is a genomic analysis predicting
GPI-anchored proteins in Arabidopsis. The paper identified RIC7 (At4g28560)
as a predicted plasma membrane receptor-like protein. The membrane
localization is consistent with this computational prediction and with
subsequent experimental evidence.
action: KEEP_AS_NON_CORE
reason: >-
The annotation is broadly correct but nonspecific. More informative
localization terms (plasma membrane, apical plasma membrane) are available
from other annotations. The TAS evidence is based on computational
predictions of GPI-anchoring and membrane association rather than direct
experimental demonstration.
- term:
id: GO:0016020
label: membrane
evidence_type: TAS
original_reference_id: PMID:12805588
qualifier: located_in
review:
summary: >-
PMID:12805588 (Borner et al. 2003) is a proteomic and genomic analysis of
GPI-anchored proteins in Arabidopsis that identified receptor-like proteins
including those at the At4g28560 locus. The membrane annotation is consistent
with these findings.
action: KEEP_AS_NON_CORE
reason: >-
Same rationale as the other membrane annotations. The annotation is correct
but subsumed by more specific plasma membrane and apical plasma membrane
annotations from direct experimental evidence.
- term:
id: GO:0009507
label: chloroplast
evidence_type: ISM
original_reference_id: GO_REF:0000122
qualifier: located_in
review:
summary: >-
The chloroplast localization is based on AtSubP computational prediction
(ISM evidence). There is no experimental evidence supporting chloroplast
localization for RIC7. Experimental studies show RIC7 localizes to the
nucleus in dark conditions and translocates to the plasma membrane upon light
stimulation or ROP2 activation (Hong et al. 2016). The protein has a
predicted signal peptide and transmembrane domain consistent with secretory
pathway/membrane targeting rather than chloroplast import.
action: MARK_AS_OVER_ANNOTATED
reason: >-
The computational prediction of chloroplast localization is not supported by
any experimental evidence. Direct confocal microscopy shows nuclear and
plasma membrane localization in guard cells, with no indication of
chloroplast targeting. The predicted signal peptide is more consistent with
ER/plasma membrane trafficking than chloroplast import.
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:11752391
qualifier: enables
review:
summary: >-
PMID:11752391 (Wu et al. 2001) identified RIC7 as one of 11 RIC proteins
that interact with Rop GTPases via their CRIB motif, using yeast two-hybrid
screening. The with/from column indicates AT3G51300 (ROP3/ARAC1). The
protein binding annotation captures this ROP GTPase interaction but is
uninformative about the specific nature of the interaction.
action: MODIFY
reason: >-
Protein binding (GO:0005515) is too generic per GO curation guidelines. RIC7
specifically binds activated ROP GTPases through its CRIB domain. A more
informative annotation would be small GTPase binding (GO:0031267), which
accurately describes the ROP GTPase interaction demonstrated by yeast
two-hybrid assays and confirmed by subsequent studies.
proposed_replacement_terms:
- id: GO:0031267
label: small GTPase binding
- term:
id: GO:0009860
label: pollen tube growth
evidence_type: IMP
original_reference_id: PMID:11752391
qualifier: acts_upstream_of_or_within
review:
summary: >-
Wu et al. (2001) showed that overexpression of RIC7 in tobacco pollen tubes
causes growth inhibition, demonstrating a role in pollen tube growth. The IMP
evidence is appropriate for this overexpression phenotype. While later studies
(Hong et al. 2016) established RIC7's primary biological role in guard cell
stomatal regulation, the pollen tube growth involvement is experimentally
supported.
action: KEEP_AS_NON_CORE
reason: >-
The annotation is experimentally supported by pollen tube overexpression
assays, but the primary characterized biological role of RIC7 is in guard
cell stomatal regulation, not pollen tube growth. The pollen tube phenotype
may reflect a secondary or overexpression-specific effect. The qualifier
acts_upstream_of_or_within appropriately conveys uncertainty about the
directness of involvement.
- term:
id: GO:0016324
label: apical plasma membrane
evidence_type: IDA
original_reference_id: PMID:11752391
qualifier: located_in
review:
summary: >-
Wu et al. (2001) showed localization of RIC proteins including RIC7 in
pollen tubes. The IDA evidence indicates direct observation of RIC7 at the
apical plasma membrane region. This is consistent with later findings (Hong
et al. 2016) showing RIC7 plasma membrane localization in guard cells upon
ROP activation. In pollen tubes, the apical region is where ROP GTPases are
concentrated and active.
action: ACCEPT
reason: >-
The apical plasma membrane localization in pollen tubes is supported by IDA
evidence from the original characterization study. This is consistent with
RIC7's role as a ROP effector, since ROP GTPases are enriched at the pollen
tube apex.
- term:
id: GO:0007165
label: signal transduction
evidence_type: IC
original_reference_id: PMID:11751054
qualifier: acts_upstream_of_or_within
review:
summary: >-
The signal transduction annotation is inferred by curator (IC) based on
protein binding evidence (with/from GO:0005515) and supported by a review on
LRR protein recognition motifs (PMID:11751054, Kobe & Kajava 2001). The
inference that an LRR-containing protein that binds ROP GTPases participates
in signal transduction is biologically sound. RIC7 is indeed a signaling
adaptor in the ROP2-RIC7-Exo70B1 pathway.
action: KEEP_AS_NON_CORE
reason: >-
Signal transduction is correct but very broad. RIC7 specifically participates
in ROP GTPase signaling that regulates stomatal movement. The annotation is
not wrong but does not capture the specific signaling pathway. The IC
evidence and general review reference are appropriate for this level of
annotation.
references:
- id: GO_REF:0000033
title: Annotation inferences using phylogenetic trees
findings: []
- id: GO_REF:0000044
title: >-
Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
vocabulary mapping, accompanied by conservative changes to GO terms applied by
UniProt
findings: []
- id: GO_REF:0000122
title: AtSubP analysis
findings: []
- id: PMID:11751054
title: The leucine-rich repeat as a protein recognition motif.
findings:
- statement: >-
General review on LRR domains as protein-protein interaction scaffolds; used
as basis for IC inference that LRR/CRIB-containing RIC7 participates in
signal transduction.
- id: PMID:11752391
title: >-
A genome-wide analysis of Arabidopsis Rop-interactive CRIB motif-containing
proteins that act as Rop GTPase targets.
findings:
- statement: >-
Primary study identifying all 11 RIC proteins in Arabidopsis. RIC7 was shown
to interact with GTP-bound ROP1 via its CRIB motif in yeast two-hybrid
assays. Overexpression in tobacco pollen tubes caused growth inhibition.
RIC7 was localized to the apical plasma membrane in pollen tubes.
supporting_text: >-
we have identified 11 Arabidopsis genes encoding novel proteins, termed RICs
(for Rop-interactive CRIB motif-containing proteins), that contain a CRIB
(for Cdc42/Rac-interactive binding) motif required for their specific
interaction with GTP-bound Rop1
- id: PMID:12068095
title: >-
Prediction of glycosylphosphatidylinositol-anchored proteins in Arabidopsis.
A genomic analysis.
findings:
- statement: >-
Genomic analysis predicting GPI-anchored proteins in Arabidopsis, including
plasma membrane receptors. At4g28560/RIC7 was identified in this analysis as
a predicted membrane-associated receptor-like protein.
- id: PMID:12805588
title: >-
Identification of glycosylphosphatidylinositol-anchored proteins in
Arabidopsis. A proteomic and genomic analysis.
findings:
- statement: >-
Follow-up proteomic validation of predicted GPI-anchored proteins in
Arabidopsis. Receptor-like proteins including those at the RIC7 locus were
identified among GPI-anchored protein candidates.
- id: file:ARATH/F4JLB7/F4JLB7-deep-research-falcon.md
title: >-
Falcon deep research report for Arabidopsis RIC7/F4JLB7, covering the
ROP2-RIC7-Exo70B1 stomatal signaling pathway
findings:
- statement: >-
Comprehensive research synthesis based on Hong et al. 2016 (New Phytologist)
and reviews on ROP signaling. Establishes RIC7 as a negative regulator of
stomatal movement that links ROP2 activity to Exo70B1-mediated vesicle
trafficking in guard cells.
core_functions:
- description: >-
RIC7 functions as a signaling adaptor downstream of ROP2 GTPase, binding
activated (GTP-bound) ROP proteins via its CRIB domain and directly inhibiting
the exocyst subunit Exo70B1. This activity negatively regulates stomatal
opening by restraining vesicle trafficking to the plasma membrane in guard
cells. RIC7 also modulates the kinetics of ABA-induced stomatal closure.
supported_by:
- reference_id: PMID:11752391
supporting_text: >-
we have identified 11 Arabidopsis genes encoding novel proteins, termed RICs
(for Rop-interactive CRIB motif-containing proteins), that contain a CRIB
(for Cdc42/Rac-interactive binding) motif required for their specific
interaction with GTP-bound Rop1
- reference_id: file:ARATH/F4JLB7/F4JLB7-deep-research-falcon.md
supporting_text: >-
RIC7 functions downstream of ROP2 and inhibits the positive stomatal-opening
factor Exo70B1, thereby restraining excess opening
molecular_function:
id: GO:0031267
label: small GTPase binding
directly_involved_in:
- id: GO:1902457
label: negative regulation of stomatal opening
- id: GO:0010119
label: regulation of stomatal movement
locations:
- id: GO:0005886
label: plasma membrane
- id: GO:0005634
label: nucleus