OsLSD1 (Q0J7V9; LOC_Os08g06280 / Os08g0159500) is the rice ortholog of the plant-specific LSD1 (LESION SIMULATING DISEASE 1) family of small C2C2-type zinc-finger proteins. Its core function is to act as a NEGATIVE regulator of plant programmed cell death (PCD) and of the hypersensitive response (HR): it restrains, rather than executes, cell death. Antisense suppression of OsLSD1 in rice produces a spontaneous lesion-mimic phenotype, increased pathogen-induced PR-1 expression, and an accelerated/intensified HR after inoculation with avirulent blast (Magnaporthe oryzae), exactly the runaway-cell-death signature expected of a loss-of-function in a cell-death brake (Wang et al. 2005, PMID:15915636). Consistent with the Arabidopsis paradigm, LSD1-like proteins are thought to set a ROS/PCD threshold and act antagonistically with the positive regulator LOL1. Secondarily, OsLSD1 is a POSITIVE regulator of callus differentiation/regeneration: 35S-driven overexpression accelerates differentiation of transformed rice calli (from ~7-10 days to ~3-5 days) and increases chlorophyll b content. The OsLSD1-GFP fusion localizes to the nucleus, consistent with a regulatory (rather than catalytic) role in nuclear protein complexes controlling cell-death commitment. The three conserved C2C2 motifs are zinc-finger motifs (the protein is named "Putative zinc finger LSD1"), implying zinc-ion binding, though direct biochemical demonstration of metal binding for the rice protein is lacking. Note that this rice OsLSD1 is unrelated to the mammalian lysine-specific demethylase LSD1/KDM1A (a name collision only).
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0006952 defense response | IEA GO_REF:0000043 | MARK AS OVER ANNOTATED | Summary: SPKW (GO_REF:0000043) annotation derived from the UniProt keyword "Plant defense"; snapshot-only, removed in the current GOA release. OsLSD1 acts in the defense/HR context, but its specific role is to NEGATIVELY regulate the defense response, not to execute defense directly. Reason: GOA's removal of this keyword-derived annotation was JUSTIFIED. "Defense response" is a broad parent term, and as a bare keyword annotation it both lacks specificity and conflates the direction of OsLSD1's role. The experimental evidence shows OsLSD1 RESTRAINS defense cell death: antisense (knockdown) plants show a lesion-mimic phenotype, increased PR-1 expression and an accelerated HR to avirulent blast, i.e. de-repressed defense responses [PMID:15915636]. The current (2026) GOA already captures this precisely and direction-aware with the IMP term "negative regulation of defense response" (GO:0031348). The generic "defense response" SPKW term therefore adds no information beyond the retained curated annotation and risks implying OsLSD1 is a positive defense effector; its removal is appropriate. Supporting Evidence: PMID:15915636 plants exhibited lesion mimic phenotype, increased expression of PR-1 mRNA, and file:ORYSJ/LSD1/LSD1-deep-research-falcon.md antisense suppression of OsLSD1 produced a **lesion mimic phenotype** and **accelerated HR cell death** upon inoculation with avirulent blast isolates, along with **increased PR-1 mRNA**—consistent with OsLSD1 functioning as a **negative regulator of PCD/HR-like cell death**. |
| GO:0009626 plant-type hypersensitive response | IEA GO_REF:0000043 | MODIFY | Summary: SPKW (GO_REF:0000043) annotation derived from the UniProt keyword "Hypersensitive response"; snapshot-only, removed in the current GOA release. This term implies OsLSD1 EXECUTES the HR, whereas the evidence shows it is a NEGATIVE regulator that restrains the HR. Reason: GOA's removal of this annotation was JUSTIFIED, and the term as stated is a regulatory conflation. Annotating OsLSD1 to "plant-type hypersensitive response" (the cell-death process itself) implies the protein carries out / promotes the HR. The experimental data show the opposite directionality: silencing OsLSD1 ACCELERATES and intensifies the HR (a runaway-cell-death loss-of-function phenotype), and the UniProt FUNCTION statement explicitly describes OsLSD1 as a "Negative regulator of programmed cell death and hypersensitive response (HR)" [PMID:15915636]. The correct, direction-aware term is "negative regulation of plant-type hypersensitive response" (GO:0034051), which is exactly what the current GOA retains as an IMP annotation. The SPKW term should therefore be replaced by GO:0034051 rather than dropped silently. Proposed replacements: negative regulation of plant-type hypersensitive response Supporting Evidence: PMID:15915636 plants exhibited lesion mimic phenotype, increased expression of PR-1 mRNA, and file:ORYSJ/LSD1/LSD1-deep-research-falcon.md OsLSD1 was identified specifically in this conceptual framework: a rice functional homolog of Arabidopsis LSD1 that participates in HR/PCD regulation. |
| GO:0030154 cell differentiation | IEA GO_REF:0000043 | MODIFY | Summary: SPKW (GO_REF:0000043) annotation derived from the UniProt keyword "Differentiation"; snapshot-only, removed in the current GOA release. OsLSD1 is not a general cell-fate / differentiation factor; it specifically PROMOTES callus differentiation/regeneration in tissue culture, so a bare "cell differentiation" process term mis-frames its role. Reason: GOA's removal of this generic keyword-derived term was JUSTIFIED. "Cell differentiation" (GO:0030154) is a very broad developmental process term and, as a bare keyword annotation, it neither captures the direction (OsLSD1 positively regulates differentiation) nor the specific context (callus differentiation/regeneration). The experimental basis is that 35S overexpression of OsLSD1 accelerates callus differentiation in transformed rice tissue, and the authors conclude OsLSD1 "plays a positive role in callus differentiation" [PMID:15915636]. The appropriate direction-aware term is "positive regulation of cell differentiation" (GO:0045597); the current GOA already retains the parent regulatory term "regulation of cell differentiation" (GO:0045595, IMP). The flat process term should be replaced rather than kept. Proposed replacements: positive regulation of cell differentiation Supporting Evidence: PMID:15915636 accelerated callus differentiation in transformed rice tissues and increased file:ORYSJ/LSD1/LSD1-deep-research-falcon.md These data support a model in which OsLSD1 has a **dual role**: restraining PCD while **promoting differentiation/regeneration** in tissue culture contexts. |
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: IEA annotation from the UniProt subcellular-location vocabulary mapping (GO_REF:0000044). Nuclear localization is directly confirmed in rice/tobacco by GFP imaging. Reason: Correct and strongly supported by direct experimental evidence: the OsLSD1-GFP fusion protein localizes to the nucleus, and the UniProt SUBCELLULAR LOCATION is "Nucleus" [PMID:15915636]. Nuclear localization is consistent with a regulatory role in nuclear protein complexes controlling PCD/HR commitment and differentiation. The IEA duplicates the experimental TAS annotation to the same term, which is acceptable. Supporting Evidence: PMID:15915636 OsLSD1 green fluorescent protein fusion protein was located in the nucleus of |
| GO:0005634 nucleus | TAS PMID:15915636 OsLSD1, a rice zinc finger protein, regulates programmed cel... | ACCEPT | Summary: TAS annotation citing the primary rice study (Wang et al. 2005), reporting nuclear localization of the OsLSD1-GFP fusion. Reason: Directly supported by the cited primary reference: Wang et al. reported that the OsLSD1 green fluorescent protein fusion protein was located in the nucleus of tobacco cells [PMID:15915636]. This is the core cellular-component annotation for OsLSD1 and is consistent with its function as a nuclear regulator of cell death and differentiation. Supporting Evidence: PMID:15915636 OsLSD1 green fluorescent protein fusion protein was located in the nucleus of |
| GO:0031348 negative regulation of defense response | IMP PMID:15915636 OsLSD1, a rice zinc finger protein, regulates programmed cel... | ACCEPT | Summary: IMP annotation: OsLSD1 negatively regulates the defense response, demonstrated by knockdown (antisense) phenotypes - de-repressed PR-1 expression and accelerated HR. Reason: This is a core function and is well supported by direct loss-of-function evidence in rice. Antisense (knockdown) OsLSD1 plants display a lesion-mimic phenotype, increased PR-1 mRNA, and an accelerated hypersensitive response to avirulent blast isolates - the classic de-repressed-defense signature expected when a negative regulator of the defense response is removed [PMID:15915636]. The UniProt FUNCTION statement summarizes OsLSD1 as a negative regulator of PCD and HR. The term is at an appropriate level of specificity and direction. Supporting Evidence: PMID:15915636 plants exhibited lesion mimic phenotype, increased expression of PR-1 mRNA, and file:ORYSJ/LSD1/LSD1-deep-research-falcon.md antisense suppression of OsLSD1 produced a **lesion mimic phenotype** and **accelerated HR cell death** upon inoculation with avirulent blast isolates, along with **increased PR-1 mRNA**—consistent with OsLSD1 functioning as a **negative regulator of PCD/HR-like cell death**. |
| GO:0034051 negative regulation of plant-type hypersensitive response | IMP PMID:15915636 OsLSD1, a rice zinc finger protein, regulates programmed cel... | ACCEPT | Summary: IMP annotation: OsLSD1 negatively regulates the plant-type hypersensitive response, shown by the accelerated/intensified HR in antisense-silenced plants. Reason: Core function, directly supported. Silencing OsLSD1 produces an accelerated and intensified HR to avirulent blast, and a spontaneous lesion-mimic phenotype - i.e. removing OsLSD1 releases the brake on the HR cell-death program [PMID:15915636]. This direction-aware term correctly captures OsLSD1's role as a restraint on (not executor of) the HR, and is the appropriate replacement for the retired bare SPKW "plant-type hypersensitive response" term above. Accept as a core annotation. Supporting Evidence: PMID:15915636 plants exhibited lesion mimic phenotype, increased expression of PR-1 mRNA, and PMID:15915636 this study, a rice (Oryza sativa) functional homolog of LSD1, designated OsLSD1, |
| GO:0045595 regulation of cell differentiation | IMP PMID:15915636 OsLSD1, a rice zinc finger protein, regulates programmed cel... | ACCEPT | Summary: IMP annotation: OsLSD1 regulates cell differentiation, based on overexpression accelerating callus differentiation/regeneration. The demonstrated direction is positive (promoting differentiation). Reason: Supported by direct gain-of-function evidence: 35S-driven OsLSD1 overexpression accelerated callus differentiation in transformed rice tissues, and the authors conclude OsLSD1 plays a positive role in callus differentiation [PMID:15915636]. The curated term "regulation of cell differentiation" (GO:0045595) is correct as the direction-neutral parent; the experimentally demonstrated direction is captured more precisely by the proposed "positive regulation of cell differentiation" (GO:0045597, see the MODIFY of the retired SPKW term and proposed_new_terms). This is a genuine but secondary (non-cell-death) function of OsLSD1; accept the existing curated term. Supporting Evidence: PMID:15915636 accelerated callus differentiation in transformed rice tissues and increased file:ORYSJ/LSD1/LSD1-deep-research-falcon.md These data support a model in which OsLSD1 has a **dual role**: restraining PCD while **promoting differentiation/regeneration** in tissue culture contexts. |
| GO:0043069 negative regulation of programmed cell death | IMP PMID:15915636 OsLSD1, a rice zinc finger protein, regulates programmed cel... | NEW | Summary: OsLSD1 is a negative regulator of programmed cell death (PCD) more broadly than just the HR. This is the unifying core function of the LSD1 family and is not explicitly captured by the current GOA process terms (which are restricted to defense response and the HR). Reason: The current GOA captures negative regulation of the defense response (GO:0031348) and of the HR (GO:0034051), but the LSD1 family's defining role is the more general negative regulation of programmed cell death, of which HR cell death is one trigger. OsLSD1 was identified as a functional homolog of Arabidopsis LSD1, whose antagonism with LOL1 controls oxidative-stress / ROS-associated PCD, and silencing OsLSD1 produces a spontaneous lesion-mimic (runaway-PCD) phenotype independent of pathogen, while ectopic overexpression in tobacco confers tolerance to the PCD-eliciting toxin fumonisin B1 [PMID:15915636]. The UniProt FUNCTION statement describes OsLSD1 as a "Negative regulator of programmed cell death and hypersensitive response". GO:0043069 is the appropriate, direction-aware term; IMP is justified by the antisense lesion-mimic phenotype. Supporting Evidence: PMID:15915636 plants exhibited lesion mimic phenotype, increased expression of PR-1 mRNA, and file:ORYSJ/LSD1/LSD1-deep-research-falcon.md Primary experimental work in rice indicates OsLSD1 acts largely as a **negative regulator of PCD** |
| GO:0008270 zinc ion binding | ISS PMID:15915636 OsLSD1, a rice zinc finger protein, regulates programmed cel... | NEW | Summary: OsLSD1 contains three conserved C2C2-type zinc-finger motifs and is named "Putative zinc finger LSD1", implying zinc-ion binding. The current GOA has no molecular-function term for OsLSD1. Reason: The current (2026) GOA release contains NO molecular-function annotation for OsLSD1 at all - only process and component terms. The protein's defining structural feature is its set of three internally conserved C2C2-type (CXXC...CXXC) zinc-finger motifs, shared with Arabidopsis LSD1/LOL1; the UniProt RecName includes "Putative zinc finger LSD1" and three "Putative zinc finger" regions are annotated on the sequence [PMID:15915636]. Zinc coordination by C2C2 motifs is the expected molecular function and is the most informative MF that can be assigned. Evidence is ISS (inferred from sequence/structural similarity to the characterized LSD1/LOL1 zinc fingers); direct metal-binding biochemistry for the rice protein has not been reported, so this is proposed as a sequence-based MF rather than IDA. Supporting Evidence: PMID:15915636 The Arabidopsis LSD1 and LOL1 proteins both contain three conserved zinc finger file:ORYSJ/LSD1/LSD1-deep-research-falcon.md three internally conserved C2C2-type zinc-finger motifs |
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Download this section (compressed HTML)Q: Does rice OsLSD1 directly bind zinc via its three C2C2 motifs, and is metal coordination required for its cell-death-suppressing activity?
Suggested experts: Chaozu He
Q: Is OsLSD1's negative regulation of PCD exerted through transcriptional control in the nucleus, or through cytoplasmic/scaffolding interactions (e.g. with metacaspases OsMC1-3), and does it act antagonistically with a rice LOL1 ortholog as in Arabidopsis?
Suggested experts: Jeffery L. Dangl
Q: Is the positive effect of OsLSD1 on callus differentiation mechanistically separable from its negative regulation of cell death, or a downstream consequence of suppressing culture-associated PCD?
Suggested experts: Chaozu He
Experiment: Generate clean CRISPR/Cas9 loss-of-function oslsd1 alleles (rather than antisense) and quantify spontaneous lesion formation, ROS accumulation, PR-gene expression and HR kinetics after avirulent blast challenge, under controlled light/temperature.
Hypothesis: Null oslsd1 plants show light-conditional runaway cell death and an accelerated HR, confirming OsLSD1 as a negative regulator of PCD/HR (rather than an HR effector).
Type: reverse-genetics / cell-death phenotyping
Experiment: Express and purify recombinant OsLSD1 and measure zinc binding (e.g. by ICP-MS, PAR competition or isothermal titration calorimetry) for wild-type and Cys-to-Ser zinc-finger mutants.
Hypothesis: OsLSD1 binds zinc stoichiometrically via its C2C2 motifs, and disrupting the fingers abolishes zinc binding and cell-death-suppressing function.
Type: in vitro metal-binding / structure-function assay
Experiment: Test for genetic and physical antagonism between OsLSD1 and a candidate rice LOL1 ortholog (and with OsMC1/OsMC2/OsMC3 metacaspases) using double mutants and in planta interaction assays (BiFC, co-IP) in the context of PCD induction.
Hypothesis: OsLSD1 sets a ROS/PCD threshold by antagonizing a positive regulator (LOL1-like) and by modulating metacaspase activity, paralleling the Arabidopsis LSD1/LOL1 model.
Type: genetic epistasis and protein-interaction analysis
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