SUN2 (At3g10730) is one of the two Arabidopsis thaliana C-terminal SUN (Cter-SUN) domain proteins (455 aa), the plant counterparts of animal SUN1/SUN2 and of fission yeast Sad1. It is a type II single-pass inner nuclear membrane protein with a nucleoplasmic N-terminus carrying a nuclear localization signal, a transmembrane segment, a luminal coiled-coil that mediates homo-oligomerization and heteromerization with SUN1, and a C-terminal SUN domain in the perinuclear space. The SUN domain binds the C-terminal KASH tails of plant-specific outer-nuclear-membrane KASH proteins (WIP1-3, SINE1-4, TIK) through a conserved KASH-binding pocket, forming SUN-KASH bridges (LINC complexes) that retain these proteins, and via WIPs the RanGTPase-activating protein RanGAP1, at the nuclear envelope. Through the WIP-bound tail-anchored WIT2 protein and the actin-based motor myosin XI-i, the bridge couples the actomyosin cytoskeleton to the nucleus and transmits cytoplasmic forces that give epidermal, root hair and trichome nuclei their elongated shape; on the nucleoplasmic side SUN proteins can also recruit the lamin-like CROWDED NUCLEI 1 (CRWN1/LINC1). SUN2 is expressed at lower levels than SUN1 but is up-regulated in proliferating tissues; it acts largely redundantly with SUN1, which predominates in nuclear shape determination, so sun2 phenotypes are seen mainly in sun1 sun2 double mutants. Together with its paralog it lines the nuclear envelope in meiotic prophase I and is needed for timely meiotic progression, full synapsis and normal crossover formation, the two paralogs attach telomeres to the nuclear envelope and drive rapid prophase chromosome movements, a conserved SUN-KASH role in meiosis. During open mitosis it follows nuclear envelope breakdown into the endoplasmic reticulum and marks the reforming nuclear envelope in coordination with the phragmoplast.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005515 protein binding | IPI PMID:19807882 Characterization of SUN-domain proteins at the higher plant ... | REMOVE | Summary: SUN2 binds SUN2 (PMID:19807882). Reason: SUN2-SUN2 self/heteromeric association via the coiled-coil domain. SUN proteins oligomerize (trimerize) as part of LINC assembly; this is already captured by the protein homo-/heterooligomerization rows, so generic protein binding adds nothing. Removal does not dispute the reported interaction. Supporting Evidence: PMID:19807882 AtSUN1 and AtSUN2 are present as homomers and heteromers in vivo, and that the coiled-coil domains are required for this |
| GO:0005515 protein binding | IPI PMID:19807882 Characterization of SUN-domain proteins at the higher plant ... | REMOVE | Summary: SUN2 binds SUN1 (PMID:19807882). Reason: SUN2-SUN1 self/heteromeric association via the coiled-coil domain. SUN proteins oligomerize (trimerize) as part of LINC assembly; this is already captured by the protein homo-/heterooligomerization rows, so generic protein binding adds nothing. Removal does not dispute the reported interaction. Supporting Evidence: PMID:19807882 AtSUN1 and AtSUN2 are present as homomers and heteromers in vivo, and that the coiled-coil domains are required for this |
| GO:0005515 protein binding | IPI PMID:19807882 Characterization of SUN-domain proteins at the higher plant ... | REMOVE | Summary: SUN2 binds SUN1 (PMID:19807882). Reason: SUN2-SUN1 self/heteromeric association via the coiled-coil domain. SUN proteins oligomerize (trimerize) as part of LINC assembly; this is already captured by the protein homo-/heterooligomerization rows, so generic protein binding adds nothing. Removal does not dispute the reported interaction. Supporting Evidence: PMID:19807882 AtSUN1 and AtSUN2 are present as homomers and heteromers in vivo, and that the coiled-coil domains are required for this |
| GO:0005515 protein binding | IPI PMID:22270916 Novel plant SUN-KASH bridges are involved in RanGAP anchorin... | MODIFY | Summary: SUN2 binds the plant KASH-domain protein WIP1 (PMID:22270916). Reason: Generic protein binding is uninformative. WIP1 is a plant outer-nuclear-membrane KASH protein whose C-terminal KASH tail is bound in the perinuclear space by the SUN domain (the conserved KASH-binding pocket, H/Y mutations of which abolish binding). This is the SUN side of a plant SUN-KASH bridge (SUN-WIP-WIT2-myosin XI-i connecting to the actomyosin cytoskeleton), which is captured by GO:0140444 cytoskeleton-nuclear membrane anchor activity, the term used for human SUN1/SUN2 KASH-binding rows. GO has no KASH-domain-binding MF term. Proposed replacements: cytoskeleton-nuclear membrane anchor activity Supporting Evidence: PMID:22270916 Here, we show that AtWIP1, AtWIP2, and AtWIP3 interact with AtSUN1 and AtSUN2 at the NE PMID:22270916 Hence, the SUN domain is essential for interacting with AtWIP1 PMID:25759303 supporting the existence of LINC complexes comprised of SUN, WIP, WIT2 and myosin XI-i |
| GO:0005515 protein binding | IPI PMID:22270916 Novel plant SUN-KASH bridges are involved in RanGAP anchorin... | MODIFY | Summary: SUN2 binds the plant KASH-domain protein WIP3 (PMID:22270916). Reason: Generic protein binding is uninformative. WIP3 is a plant outer-nuclear-membrane KASH protein whose C-terminal KASH tail is bound in the perinuclear space by the SUN domain (the conserved KASH-binding pocket, H/Y mutations of which abolish binding). This is the SUN side of a plant SUN-KASH bridge (SUN-WIP-WIT2-myosin XI-i connecting to the actomyosin cytoskeleton), which is captured by GO:0140444 cytoskeleton-nuclear membrane anchor activity, the term used for human SUN1/SUN2 KASH-binding rows. GO has no KASH-domain-binding MF term. Proposed replacements: cytoskeleton-nuclear membrane anchor activity Supporting Evidence: PMID:22270916 Here, we show that AtWIP1, AtWIP2, and AtWIP3 interact with AtSUN1 and AtSUN2 at the NE PMID:22270916 Hence, the SUN domain is essential for interacting with AtWIP1 PMID:25759303 supporting the existence of LINC complexes comprised of SUN, WIP, WIT2 and myosin XI-i |
| GO:0005515 protein binding | IPI PMID:22270916 Novel plant SUN-KASH bridges are involved in RanGAP anchorin... | MODIFY | Summary: SUN2 binds the plant KASH-domain protein WIP2 (PMID:22270916). Reason: Generic protein binding is uninformative. WIP2 is a plant outer-nuclear-membrane KASH protein whose C-terminal KASH tail is bound in the perinuclear space by the SUN domain (the conserved KASH-binding pocket, H/Y mutations of which abolish binding). This is the SUN side of a plant SUN-KASH bridge (SUN-WIP-WIT2-myosin XI-i connecting to the actomyosin cytoskeleton), which is captured by GO:0140444 cytoskeleton-nuclear membrane anchor activity, the term used for human SUN1/SUN2 KASH-binding rows. GO has no KASH-domain-binding MF term. Proposed replacements: cytoskeleton-nuclear membrane anchor activity Supporting Evidence: PMID:22270916 Here, we show that AtWIP1, AtWIP2, and AtWIP3 interact with AtSUN1 and AtSUN2 at the NE PMID:22270916 Hence, the SUN domain is essential for interacting with AtWIP1 PMID:25759303 supporting the existence of LINC complexes comprised of SUN, WIP, WIT2 and myosin XI-i |
| GO:0005515 protein binding | IPI PMID:23973298 Myosin XI-i links the nuclear membrane to the cytoskeleton t... | MODIFY | Summary: SUN2 binds the plant KASH-domain protein WIP1 (PMID:23973298). Reason: Generic protein binding is uninformative. WIP1 is a plant outer-nuclear-membrane KASH protein whose C-terminal KASH tail is bound in the perinuclear space by the SUN domain (the conserved KASH-binding pocket, H/Y mutations of which abolish binding). This is the SUN side of a plant SUN-KASH bridge (SUN-WIP-WIT2-myosin XI-i connecting to the actomyosin cytoskeleton), which is captured by GO:0140444 cytoskeleton-nuclear membrane anchor activity, the term used for human SUN1/SUN2 KASH-binding rows. GO has no KASH-domain-binding MF term. The cited paper is abstract-only in our cache and its abstract does not describe the WIP1 interaction, but the SUN-WIP1 interaction is independently and directly established (PMID:22270916, PMID:24891605), so the curator's assertion is not in doubt. Proposed replacements: cytoskeleton-nuclear membrane anchor activity Supporting Evidence: PMID:22270916 Here, we show that AtWIP1, AtWIP2, and AtWIP3 interact with AtSUN1 and AtSUN2 at the NE PMID:22270916 Hence, the SUN domain is essential for interacting with AtWIP1 PMID:25759303 supporting the existence of LINC complexes comprised of SUN, WIP, WIT2 and myosin XI-i |
| GO:0005515 protein binding | IPI PMID:24667841 Evidence for LINC1-SUN associations at the plant nuclear per... | REMOVE | Summary: SUN2 associates with the lamin-analogous nucleoskeletal protein CRWN1/LINC1 (FRET-FLIM, FRAP). Reason: Generic protein binding is uninformative. CRWN1 is a plant lamin analogue, not a lamin homologue, so GO:0005521 lamin binding would not be accurate. The functional consequence (SUN-dependent recruitment and immobilisation of CRWN1 at the NE) is captured by the GO:0090435 protein localization to nuclear envelope row from the same paper. Removal does not dispute the interaction. Supporting Evidence: PMID:24667841 AtLINC1 is recruited to the NE by SUN proteins and is immobilised therein PMID:24667841 SUN-dependent NE localisation and immobilisation of LINC1 as well as LINC1-SUN interactions at the NE are strong indicators that SUN proteins are involved in nucleoskeletal anchorage at the plant NE |
| GO:0005515 protein binding | IPI PMID:24891605 Identification of unique SUN-interacting nuclear envelope pr... | MODIFY | Summary: SUN2 binds the plant KASH-domain protein SINE1 (PMID:24891605). Reason: Generic protein binding is uninformative. SINE1 is a plant outer-nuclear-membrane KASH protein whose C-terminal KASH tail is bound in the perinuclear space by the SUN domain (the conserved KASH-binding pocket, H/Y mutations of which abolish binding). This is the SUN side of a plant SUN-KASH bridge (SUN-WIP-WIT2-myosin XI-i connecting to the actomyosin cytoskeleton), which is captured by GO:0140444 cytoskeleton-nuclear membrane anchor activity, the term used for human SUN1/SUN2 KASH-binding rows. GO has no KASH-domain-binding MF term. Proposed replacements: cytoskeleton-nuclear membrane anchor activity Supporting Evidence: PMID:24891605 Together, these data indicate that SINE1 and SINE2 interact with AtSUN1 and AtSUN2 at the plant NE PMID:24891605 SINE3 strongly binds to AtSUN1 and AtSUN2 PMID:24891605 confirming that the KASH-binding pocket within the SUN domain is required for interaction |
| GO:0005515 protein binding | IPI PMID:24891605 Identification of unique SUN-interacting nuclear envelope pr... | MODIFY | Summary: SUN2 binds the plant KASH-domain protein SINE3 (PMID:24891605). Reason: Generic protein binding is uninformative. SINE3 is a plant outer-nuclear-membrane KASH protein whose C-terminal KASH tail is bound in the perinuclear space by the SUN domain (the conserved KASH-binding pocket, H/Y mutations of which abolish binding). This is the SUN side of a plant SUN-KASH bridge (SUN-WIP-WIT2-myosin XI-i connecting to the actomyosin cytoskeleton), which is captured by GO:0140444 cytoskeleton-nuclear membrane anchor activity, the term used for human SUN1/SUN2 KASH-binding rows. GO has no KASH-domain-binding MF term. Proposed replacements: cytoskeleton-nuclear membrane anchor activity Supporting Evidence: PMID:24891605 Together, these data indicate that SINE1 and SINE2 interact with AtSUN1 and AtSUN2 at the plant NE PMID:24891605 SINE3 strongly binds to AtSUN1 and AtSUN2 PMID:24891605 confirming that the KASH-binding pocket within the SUN domain is required for interaction |
| GO:0005515 protein binding | IPI PMID:24891605 Identification of unique SUN-interacting nuclear envelope pr... | MODIFY | Summary: SUN2 binds the plant KASH-domain protein SINE2 (PMID:24891605). Reason: Generic protein binding is uninformative. SINE2 is a plant outer-nuclear-membrane KASH protein whose C-terminal KASH tail is bound in the perinuclear space by the SUN domain (the conserved KASH-binding pocket, H/Y mutations of which abolish binding). This is the SUN side of a plant SUN-KASH bridge (SUN-WIP-WIT2-myosin XI-i connecting to the actomyosin cytoskeleton), which is captured by GO:0140444 cytoskeleton-nuclear membrane anchor activity, the term used for human SUN1/SUN2 KASH-binding rows. GO has no KASH-domain-binding MF term. Proposed replacements: cytoskeleton-nuclear membrane anchor activity Supporting Evidence: PMID:24891605 Together, these data indicate that SINE1 and SINE2 interact with AtSUN1 and AtSUN2 at the plant NE PMID:24891605 SINE3 strongly binds to AtSUN1 and AtSUN2 PMID:24891605 confirming that the KASH-binding pocket within the SUN domain is required for interaction |
| GO:0005515 protein binding | IPI PMID:24891605 Identification of unique SUN-interacting nuclear envelope pr... | MODIFY | Summary: SUN2 binds the plant KASH-domain protein SINE4 (PMID:24891605). Reason: Generic protein binding is uninformative. SINE4 is a plant outer-nuclear-membrane KASH protein whose C-terminal KASH tail is bound in the perinuclear space by the SUN domain (the conserved KASH-binding pocket, H/Y mutations of which abolish binding). This is the SUN side of a plant SUN-KASH bridge (SUN-WIP-WIT2-myosin XI-i connecting to the actomyosin cytoskeleton), which is captured by GO:0140444 cytoskeleton-nuclear membrane anchor activity, the term used for human SUN1/SUN2 KASH-binding rows. GO has no KASH-domain-binding MF term. Proposed replacements: cytoskeleton-nuclear membrane anchor activity Supporting Evidence: PMID:24891605 Together, these data indicate that SINE1 and SINE2 interact with AtSUN1 and AtSUN2 at the plant NE PMID:24891605 SINE3 strongly binds to AtSUN1 and AtSUN2 PMID:24891605 confirming that the KASH-binding pocket within the SUN domain is required for interaction |
| GO:0005515 protein binding | IPI PMID:25217773 Characterization of two distinct subfamilies of SUN-domain p... | REMOVE | Summary: SUN2 binds SUN3 (PMID:25217773). Reason: Interaction of SUN2 with the mid-SUN protein SUN3 (Y2H/in planta, coiled-coil mediated). This is a physical association whose functional meaning is unknown; generic protein binding adds no functional information. Removal does not dispute the reported interaction. Supporting Evidence: PMID:25217773 We investigated interactions in and between members of the two subfamilies and identified the coiled-coil domain as necessary for mediating interactions |
| GO:0005515 protein binding | IPI PMID:25217773 Characterization of two distinct subfamilies of SUN-domain p... | REMOVE | Summary: SUN2 binds SUN4 (PMID:25217773). Reason: Interaction of SUN2 with the mid-SUN protein SUN4 (Y2H/in planta, coiled-coil mediated). This is a physical association whose functional meaning is unknown; generic protein binding adds no functional information. Removal does not dispute the reported interaction. Supporting Evidence: PMID:25217773 We investigated interactions in and between members of the two subfamilies and identified the coiled-coil domain as necessary for mediating interactions |
| GO:0005515 protein binding | IPI PMID:25217773 Characterization of two distinct subfamilies of SUN-domain p... | MODIFY | Summary: SUN2 binds the plant KASH-domain protein TIK (PMID:25217773). Reason: Generic protein binding is uninformative. TIK is a plant outer-nuclear-membrane KASH protein whose C-terminal KASH tail is bound in the perinuclear space by the SUN domain (the conserved KASH-binding pocket, H/Y mutations of which abolish binding). This is the SUN side of a plant SUN-KASH bridge (SUN-WIP-WIT2-myosin XI-i connecting to the actomyosin cytoskeleton), which is captured by GO:0140444 cytoskeleton-nuclear membrane anchor activity, the term used for human SUN1/SUN2 KASH-binding rows. GO has no KASH-domain-binding MF term. Proposed replacements: cytoskeleton-nuclear membrane anchor activity Supporting Evidence: PMID:25217773 both subfamilies interact with the KASH domain of AtWIP1 and identified a new root-specific KASH-domain protein, AtTIK |
| GO:0005515 protein binding | IPI PMID:25217773 Characterization of two distinct subfamilies of SUN-domain p... | REMOVE | Summary: SUN2 binds SUN1 (PMID:25217773). Reason: SUN2-SUN1 self/heteromeric association via the coiled-coil domain. SUN proteins oligomerize (trimerize) as part of LINC assembly; this is already captured by the protein homo-/heterooligomerization rows, so generic protein binding adds nothing. Removal does not dispute the reported interaction. Supporting Evidence: PMID:19807882 AtSUN1 and AtSUN2 are present as homomers and heteromers in vivo, and that the coiled-coil domains are required for this |
| GO:0005515 protein binding | IPI PMID:25330379 The kinesin AtPSS1 promotes synapsis and is required for pro... | REMOVE | Summary: SUN2 binds SUN1 (PMID:25330379). Reason: SUN2-SUN1 self/heteromeric association via the coiled-coil domain. SUN proteins oligomerize (trimerize) as part of LINC assembly; this is already captured by the protein homo-/heterooligomerization rows, so generic protein binding adds nothing. Removal does not dispute the reported interaction. Supporting Evidence: PMID:19807882 AtSUN1 and AtSUN2 are present as homomers and heteromers in vivo, and that the coiled-coil domains are required for this |
| GO:0005515 protein binding | IPI PMID:27630107 A novel family of plant nuclear envelope-associated proteins... | MODIFY | Summary: SUN2 binds the plant KASH-domain protein SINE3 (PMID:27630107). Reason: Generic protein binding is uninformative. SINE3 is a plant outer-nuclear-membrane KASH protein whose C-terminal KASH tail is bound in the perinuclear space by the SUN domain (the conserved KASH-binding pocket, H/Y mutations of which abolish binding). This is the SUN side of a plant SUN-KASH bridge (SUN-WIP-WIT2-myosin XI-i connecting to the actomyosin cytoskeleton), which is captured by GO:0140444 cytoskeleton-nuclear membrane anchor activity, the term used for human SUN1/SUN2 KASH-binding rows. GO has no KASH-domain-binding MF term. The cited paper is abstract-only in our cache and its abstract does not describe the SINE3 interaction, but the SUN-SINE interaction is independently and directly established (PMID:22270916, PMID:24891605), so the curator's assertion is not in doubt. Proposed replacements: cytoskeleton-nuclear membrane anchor activity Supporting Evidence: PMID:27630107 interact with the SUN domain proteins AtSUN1 and AtSUN2 PMID:24891605 Together, these data indicate that SINE1 and SINE2 interact with AtSUN1 and AtSUN2 at the plant NE PMID:24891605 SINE3 strongly binds to AtSUN1 and AtSUN2 PMID:24891605 confirming that the KASH-binding pocket within the SUN domain is required for interaction |
| GO:0005515 protein binding | IPI PMID:27630107 A novel family of plant nuclear envelope-associated proteins... | REMOVE | Summary: SUN2 interacts with NEAP1, a coiled-coil inner-nuclear-membrane protein. Reason: Generic protein binding is uninformative; NEAP1 is a plant-specific coiled-coil INM protein and no more specific activity of the SUN-NEAP association has been defined. Removal does not dispute the reported interaction. Supporting Evidence: PMID:27630107 interact with the SUN domain proteins AtSUN1 and AtSUN2 |
| GO:0005515 protein binding | IPI PMID:27630107 A novel family of plant nuclear envelope-associated proteins... | MODIFY | Summary: SUN2 binds the plant KASH-domain protein SINE2 (PMID:27630107). Reason: Generic protein binding is uninformative. SINE2 is a plant outer-nuclear-membrane KASH protein whose C-terminal KASH tail is bound in the perinuclear space by the SUN domain (the conserved KASH-binding pocket, H/Y mutations of which abolish binding). This is the SUN side of a plant SUN-KASH bridge (SUN-WIP-WIT2-myosin XI-i connecting to the actomyosin cytoskeleton), which is captured by GO:0140444 cytoskeleton-nuclear membrane anchor activity, the term used for human SUN1/SUN2 KASH-binding rows. GO has no KASH-domain-binding MF term. The cited paper is abstract-only in our cache and its abstract does not describe the SINE2 interaction, but the SUN-SINE interaction is independently and directly established (PMID:22270916, PMID:24891605), so the curator's assertion is not in doubt. Proposed replacements: cytoskeleton-nuclear membrane anchor activity Supporting Evidence: PMID:27630107 interact with the SUN domain proteins AtSUN1 and AtSUN2 PMID:24891605 Together, these data indicate that SINE1 and SINE2 interact with AtSUN1 and AtSUN2 at the plant NE PMID:24891605 SINE3 strongly binds to AtSUN1 and AtSUN2 PMID:24891605 confirming that the KASH-binding pocket within the SUN domain is required for interaction |
| GO:0005634 nucleus | ISM GO_REF:0000122 | ACCEPT | Summary: Nucleus (AtSubP prediction). Reason: Correct but general: SUN2 is an inner-nuclear-membrane protein with a functional NLS, so it is part of the nucleus. The experimentally supported, more specific location is nuclear inner membrane. Supporting Evidence: PMID:19807882 localize to and show low mobility in the nuclear envelope (NE), particularly in the INM |
| GO:0005635 nuclear envelope | HDA PMID:15469496 Molecular dissection of plant cytokinesis and phragmoplast s... | ACCEPT | Summary: Nuclear envelope, from a GFP-fusion localization survey of cytokinesis candidates. Reason: Abstract-only in cache and the abstract does not list individual proteins, but NE localization of Arabidopsis Cter-SUN proteins is independently and repeatedly established. Supporting Evidence: PMID:19807882 localize to and show low mobility in the nuclear envelope (NE), particularly in the INM |
| GO:0005635 nuclear envelope | IBA GO_REF:0000033 | ACCEPT | Summary: Nuclear envelope (PAINT, SUN family node PTN000308195). Reason: Sound phylogenetic inference; Arabidopsis SUN1 and SUN2 themselves are among the experimental descendants that ground the node, and SUN2 is an established NE protein. Supporting Evidence: PMID:19807882 localize to and show low mobility in the nuclear envelope (NE), particularly in the INM |
| GO:0005635 nuclear envelope | IDA PMID:19807882 Characterization of SUN-domain proteins at the higher plant ... | ACCEPT | Summary: Nuclear envelope, from fluorescent-protein fusion or immunolocalization (PMID:19807882). Reason: SUN2 is a C-terminal SUN (Cter-SUN) protein enriched at the nuclear envelope in somatic and meiotic cells; the NE is where it performs its LINC function. Supporting Evidence: PMID:19807882 localize to and show low mobility in the nuclear envelope (NE), particularly in the INM |
| GO:0005635 nuclear envelope | IDA PMID:21294795 Dynamics of Arabidopsis SUN proteins during mitosis and thei... | ACCEPT | Summary: Nuclear envelope, from fluorescent-protein fusion or immunolocalization (PMID:21294795). Reason: SUN2 is a C-terminal SUN (Cter-SUN) protein enriched at the nuclear envelope in somatic and meiotic cells; the NE is where it performs its LINC function. Supporting Evidence: PMID:21294795 The localizations of SUN proteins changed dynamically during mitosis, tightly coupled with NE dynamics |
| GO:0005635 nuclear envelope | IDA PMID:22270916 Novel plant SUN-KASH bridges are involved in RanGAP anchorin... | ACCEPT | Summary: Nuclear envelope, from fluorescent-protein fusion or immunolocalization (PMID:22270916). Reason: SUN2 is a C-terminal SUN (Cter-SUN) protein enriched at the nuclear envelope in somatic and meiotic cells; the NE is where it performs its LINC function. Supporting Evidence: PMID:22270916 Here, we show that AtWIP1, AtWIP2, and AtWIP3 interact with AtSUN1 and AtSUN2 at the NE |
| GO:0005635 nuclear envelope | IDA PMID:24667841 Evidence for LINC1-SUN associations at the plant nuclear per... | ACCEPT | Summary: Nuclear envelope, from fluorescent-protein fusion or immunolocalization (PMID:24667841). Reason: SUN2 is a C-terminal SUN (Cter-SUN) protein enriched at the nuclear envelope in somatic and meiotic cells; the NE is where it performs its LINC function. Supporting Evidence: PMID:24667841 AtLINC1 is recruited to the NE by SUN proteins and is immobilised therein |
| GO:0005635 nuclear envelope | IDA PMID:25412930 Absence of SUN1 and SUN2 proteins in Arabidopsis thaliana le... | ACCEPT | Summary: Nuclear envelope, from fluorescent-protein fusion or immunolocalization (PMID:25412930). Reason: SUN2 is a C-terminal SUN (Cter-SUN) protein enriched at the nuclear envelope in somatic and meiotic cells; the NE is where it performs its LINC function. Supporting Evidence: PMID:25412930 Immunolocalization using antibodies against AtSUN1 and AtSUN2 proteins revealed that they were associated with the nuclear envelope during meiotic prophase I |
| GO:0005635 nuclear envelope | IEA GO_REF:0000044 | ACCEPT | Summary: Nuclear envelope (UniProt subcellular location mapping). Reason: Consistent with extensive experimental data. Supporting Evidence: PMID:19807882 localize to and show low mobility in the nuclear envelope (NE), particularly in the INM |
| GO:0005637 nuclear inner membrane | EXP PMID:19807882 Characterization of SUN-domain proteins at the higher plant ... | ACCEPT | Summary: Nuclear inner membrane (PMID:19807882). Reason: SUN2 is a type II single-pass inner-nuclear-membrane protein whose SUN domain lies in the perinuclear space, as for all Cter-SUN proteins; INM enrichment was shown with FP fusions and antibodies. Supporting Evidence: PMID:19807882 localize to and show low mobility in the nuclear envelope (NE), particularly in the INM |
| GO:0005637 nuclear inner membrane | EXP PMID:21294795 Dynamics of Arabidopsis SUN proteins during mitosis and thei... | ACCEPT | Summary: Nuclear inner membrane (PMID:21294795). Reason: SUN2 is a type II single-pass inner-nuclear-membrane protein whose SUN domain lies in the perinuclear space, as for all Cter-SUN proteins; INM enrichment was shown with FP fusions and antibodies. Supporting Evidence: PMID:21294795 The localizations of SUN proteins changed dynamically during mitosis, tightly coupled with NE dynamics |
| GO:0005637 nuclear inner membrane | EXP PMID:24667841 Evidence for LINC1-SUN associations at the plant nuclear per... | ACCEPT | Summary: Nuclear inner membrane (PMID:24667841). Reason: SUN2 is a type II single-pass inner-nuclear-membrane protein whose SUN domain lies in the perinuclear space, as for all Cter-SUN proteins; INM enrichment was shown with FP fusions and antibodies. Supporting Evidence: PMID:24667841 SUN-dependent NE localisation and immobilisation of LINC1 as well as LINC1-SUN interactions at the NE are strong indicators that SUN proteins are involved in nucleoskeletal anchorage at the plant NE |
| GO:0005637 nuclear inner membrane | EXP PMID:25412930 Absence of SUN1 and SUN2 proteins in Arabidopsis thaliana le... | ACCEPT | Summary: Nuclear inner membrane (PMID:25412930). Reason: SUN2 is a type II single-pass inner-nuclear-membrane protein whose SUN domain lies in the perinuclear space, as for all Cter-SUN proteins; INM enrichment was shown with FP fusions and antibodies. Supporting Evidence: PMID:25412930 Immunolocalization using antibodies against AtSUN1 and AtSUN2 proteins revealed that they were associated with the nuclear envelope during meiotic prophase I |
| GO:0005637 nuclear inner membrane | IEA GO_REF:0000120 | ACCEPT | Summary: Nuclear inner membrane (ARBA/SubCell). Reason: Consistent with experimental INM localization and type II topology (nucleoplasmic N-terminus, luminal SUN domain). Supporting Evidence: PMID:19807882 localize to and show low mobility in the nuclear envelope (NE), particularly in the INM |
| GO:0005783 endoplasmic reticulum | HDA PMID:16618929 Mapping the Arabidopsis organelle proteome. | KEEP AS NON CORE | Summary: endoplasmic reticulum from organelle proteomics (LOPIT). Reason: High-throughput density-gradient assignment; the NE membrane is continuous with the ER so NE proteins co-fractionate with ER. Not incorrect, but the functional location is the inner nuclear membrane. Supporting Evidence: PMID:25217773 localize to the nuclear envelope (NE) and endoplasmic reticulum. However, only the Cter-SUN subfamily is enriched at the NE |
| GO:0005783 endoplasmic reticulum | HDA PMID:22923678 Putative glycosyltransferases and other plant Golgi apparatu... | KEEP AS NON CORE | Summary: endoplasmic reticulum from organelle proteomics (LOPIT). Reason: High-throughput density-gradient assignment; the NE membrane is continuous with the ER so NE proteins co-fractionate with ER. Not incorrect, but the functional location is the inner nuclear membrane. Supporting Evidence: PMID:25217773 localize to the nuclear envelope (NE) and endoplasmic reticulum. However, only the Cter-SUN subfamily is enriched at the NE |
| GO:0005789 endoplasmic reticulum membrane | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: endoplasmic reticulum membrane (UniProt subcellular location mapping). Reason: Reflects the mitotic ER localization; not the functional location. Supporting Evidence: file:ARATH/SUN2/SUN2-uniprot.txt predominantly localized with the endoplasmic reticulum |
| GO:0005789 endoplasmic reticulum membrane | ISS PMID:21294795 Dynamics of Arabidopsis SUN proteins during mitosis and thei... | KEEP AS NON CORE | Summary: endoplasmic reticulum membrane: after NE breakdown in mitosis SUN2 relocates to the ER. Reason: Genuine but transient location during open mitosis (and a pool seen with overexpressed fusions); the functional location is the NE/INM. Supporting Evidence: PMID:21294795 The localizations of SUN proteins changed dynamically during mitosis, tightly coupled with NE dynamics file:ARATH/SUN2/SUN2-uniprot.txt predominantly localized with the endoplasmic reticulum |
| GO:0005819 spindle | HDA PMID:15469496 Molecular dissection of plant cytokinesis and phragmoplast s... | KEEP AS NON CORE | Summary: Spindle, from a high-throughput GFP localization survey. Reason: The survey (abstract-only in cache; full text paywalled) GFP-tagged more than 100 candidate cytokinesis proteins in dividing BY-2 cells. A QuickGO query for this PMID (recorded in SUN2-notes.md) shows that TAIR recorded SUN2 from this survey at the nuclear envelope, spindle and phragmoplast, i.e. a mitotic time course, and recorded SUN1 at the nuclear envelope as well. This is consistent with the dynamics described by Oda & Fukuda (2011), where SUN proteins follow NE breakdown and re-formation during open mitosis, with the membranes positioned around the spindle and later the phragmoplast. The curated HDA observation is accepted for what it is, a transient mitotic location of the SUN2 fusion, and handled the same way as the phragmoplast rows from this and the Oda & Fukuda paper; kept as non-core. It does not imply any role for SUN2 in spindle microtubule function; the functional location is the nuclear envelope/inner nuclear membrane. Supporting Evidence: PMID:21294795 The localizations of SUN proteins changed dynamically during mitosis, tightly coupled with NE dynamics file:ARATH/SUN2/SUN2-uniprot.txt predominantly localized with the endoplasmic reticulum |
| GO:0006997 nucleus organization | IEA GO_REF:0000117 | ACCEPT | Summary: Nucleus organization (ARBA). Reason: Consistent with the experimentally established role of Cter-SUN proteins in determining elongated nuclear shape. Supporting Evidence: PMID:21294795 they are necessary for the maintenance and/or formation of polarized nuclear shape in root hairs PMID:22270916 AtWIPs and AtSUNs are necessary for maintaining the elongated nuclear shape of Arabidopsis epidermal cells |
| GO:0006997 nucleus organization | IGI PMID:22270916 Novel plant SUN-KASH bridges are involved in RanGAP anchorin... | ACCEPT | Summary: Nuclear shape/organization: sun1 sun2 mutants have round, invaginated instead of elongated nuclei (PMID:22270916). Reason: SUN2 (with its paralog, SUN1 predominating) is part of the SUN-WIP-WIT2-myosin XI-i bridge that transmits cytoplasmic force to the NE to shape the nucleus; this is the best-established process role of plant Cter-SUN proteins. No more specific GO term for nuclear shape exists. Supporting Evidence: PMID:22270916 AtWIPs and AtSUNs are necessary for maintaining the elongated nuclear shape of Arabidopsis epidermal cells PMID:25759303 This supports a model of nuclei being shaped both by cytoplasmic forces transferred to the NE and by nucleoplasmic filaments formed under the NE |
| GO:0006997 nucleus organization | IMP PMID:21294795 Dynamics of Arabidopsis SUN proteins during mitosis and thei... | ACCEPT | Summary: Nuclear shape/organization: sun1 sun2 mutants have round, invaginated instead of elongated nuclei (PMID:21294795). Reason: SUN2 (with its paralog, SUN1 predominating) is part of the SUN-WIP-WIT2-myosin XI-i bridge that transmits cytoplasmic force to the NE to shape the nucleus; this is the best-established process role of plant Cter-SUN proteins. No more specific GO term for nuclear shape exists. Supporting Evidence: PMID:21294795 they are necessary for the maintenance and/or formation of polarized nuclear shape in root hairs PMID:25759303 This supports a model of nuclei being shaped both by cytoplasmic forces transferred to the NE and by nucleoplasmic filaments formed under the NE |
| GO:0009524 phragmoplast | HDA PMID:15469496 Molecular dissection of plant cytokinesis and phragmoplast s... | KEEP AS NON CORE | Summary: Phragmoplast. Reason: During telophase SUN proteins mark the reforming NE, which is spatially coordinated with the phragmoplast; the signal reflects NE reassembly membranes adjacent to/within the phragmoplast region rather than a phragmoplast microtubule function. Retained as a transient mitotic location. Supporting Evidence: PMID:21294795 NE re-formation marked with SUN proteins is temporally and spatially coordinated with plant-specific microtubule structures such as phragmoplasts |
| GO:0009524 phragmoplast | IDA PMID:21294795 Dynamics of Arabidopsis SUN proteins during mitosis and thei... | KEEP AS NON CORE | Summary: Phragmoplast. Reason: During telophase SUN proteins mark the reforming NE, which is spatially coordinated with the phragmoplast; the signal reflects NE reassembly membranes adjacent to/within the phragmoplast region rather than a phragmoplast microtubule function. Retained as a transient mitotic location. Supporting Evidence: PMID:21294795 NE re-formation marked with SUN proteins is temporally and spatially coordinated with plant-specific microtubule structures such as phragmoplasts |
| GO:0009524 phragmoplast | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: Phragmoplast. Reason: During telophase SUN proteins mark the reforming NE, which is spatially coordinated with the phragmoplast; the signal reflects NE reassembly membranes adjacent to/within the phragmoplast region rather than a phragmoplast microtubule function. Retained as a transient mitotic location. Supporting Evidence: PMID:21294795 NE re-formation marked with SUN proteins is temporally and spatially coordinated with plant-specific microtubule structures such as phragmoplasts |
| GO:0043495 protein-membrane adaptor activity | IBA GO_REF:0000033 | ACCEPT | Summary: Protein-membrane adaptor activity (PAINT, SUN family). Reason: Sound PAINT inference: SUN proteins anchor KASH proteins at the outer nuclear membrane. Arabidopsis SUN1/SUN2 appear among the experimental sources, which is expected. More general parent of GO:0140444 used in core_functions. Supporting Evidence: PMID:22270916 The interaction is required for both AtWIP1 and AtRanGAP1 NE localization PMID:22270916 the GFP-AtWIP1 signal in sun1-KO sun2-KD is predominantly diffuse in the cytoplasm |
| GO:0043495 protein-membrane adaptor activity | IDA PMID:22270916 Novel plant SUN-KASH bridges are involved in RanGAP anchorin... | ACCEPT | Summary: Protein-membrane adaptor activity: Cter-SUNs are required to retain the KASH protein WIP1 (and thereby RanGAP1) at the NE. Reason: Direct experimental support: in sun1-KO sun2-KD, GFP-WIP1 is diffuse, and SUN coexpression immobilises WIP1 at the NE via the SUN domain. This is the core SUN anchoring activity (GO:0140444 is the more specific child used in core_functions). Supporting Evidence: PMID:22270916 The interaction is required for both AtWIP1 and AtRanGAP1 NE localization PMID:22270916 the GFP-AtWIP1 signal in sun1-KO sun2-KD is predominantly diffuse in the cytoplasm PMID:22270916 Hence, the SUN domain is essential for interacting with AtWIP1 |
| GO:0043495 protein-membrane adaptor activity | IEA GO_REF:0000117 | ACCEPT | Summary: Protein-membrane adaptor activity (ARBA). Reason: Consistent with the experimental and IBA annotations. Supporting Evidence: PMID:22270916 The interaction is required for both AtWIP1 and AtRanGAP1 NE localization |
| GO:0051260 protein homooligomerization | IDA PMID:19807882 Characterization of SUN-domain proteins at the higher plant ... | KEEP AS NON CORE | Summary: protein homooligomerization: SUN2 forms homomers and SUN1-SUN2 heteromers in vivo via its coiled-coil. Reason: Well supported (FRET/FLIM in planta), and SUN oligomerization is structurally required for KASH binding, but it is an assembly property rather than the gene's biological role. Supporting Evidence: PMID:19807882 AtSUN1 and AtSUN2 are present as homomers and heteromers in vivo, and that the coiled-coil domains are required for this |
| GO:0051260 protein homooligomerization | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: protein homooligomerization: SUN2 forms homomers and SUN1-SUN2 heteromers in vivo via its coiled-coil. Reason: Well supported (FRET/FLIM in planta), and SUN oligomerization is structurally required for KASH binding, but it is an assembly property rather than the gene's biological role. Supporting Evidence: PMID:19807882 AtSUN1 and AtSUN2 are present as homomers and heteromers in vivo, and that the coiled-coil domains are required for this |
| GO:0051291 protein heterooligomerization | IDA PMID:19807882 Characterization of SUN-domain proteins at the higher plant ... | KEEP AS NON CORE | Summary: protein heterooligomerization: SUN2 forms homomers and SUN1-SUN2 heteromers in vivo via its coiled-coil. Reason: Well supported (FRET/FLIM in planta), and SUN oligomerization is structurally required for KASH binding, but it is an assembly property rather than the gene's biological role. Supporting Evidence: PMID:19807882 AtSUN1 and AtSUN2 are present as homomers and heteromers in vivo, and that the coiled-coil domains are required for this |
| GO:0051291 protein heterooligomerization | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: protein heterooligomerization: SUN2 forms homomers and SUN1-SUN2 heteromers in vivo via its coiled-coil. Reason: Well supported (FRET/FLIM in planta), and SUN oligomerization is structurally required for KASH binding, but it is an assembly property rather than the gene's biological role. Supporting Evidence: PMID:19807882 AtSUN1 and AtSUN2 are present as homomers and heteromers in vivo, and that the coiled-coil domains are required for this |
| GO:0070197 meiotic attachment of telomere to nuclear envelope | IEA GO_REF:0000117 | ACCEPT | Summary: Meiotic attachment of telomere to nuclear envelope (ARBA). Reason: Consistent with the IMP annotation from Varas et al. 2015 and the conserved meiotic SUN-KASH telomere-tethering role. Supporting Evidence: PMID:25412930 Immunolocalization using antibodies against AtSUN1 and AtSUN2 proteins revealed that they were associated with the nuclear envelope during meiotic prophase I file:ARATH/SUN2/SUN2-uniprot.txt may be involved in telomere attachment to nuclear envelope in the PMID:39013853 Our data confirmed previous results from35 that in the sun1 sun2 double mutant, telomere dynamics are strongly perturbed, and we observed that telomere association with the NE is rare in sun1 sun2, even if not wholly absent PMID:39013853 demonstrating the key role of SUN1 and SUN2 in controlling the meiotic prophase centromere movements |
| GO:0070197 meiotic attachment of telomere to nuclear envelope | IMP PMID:25412930 Absence of SUN1 and SUN2 proteins in Arabidopsis thaliana le... | ACCEPT | Summary: Meiotic telomere attachment to the NE: SUN1/SUN2 line the NE in meiotic prophase I and sun1 sun2 double mutants show delayed meiosis, incomplete synapsis, interlocks and fewer chiasmata. Reason: Abstract-only in cache; the abstract reports NE localization and synapsis/recombination defects. The TAIR curator read the full text, and a later study (PMID:39013853, full text) confirms that telomere association with the NE is rare in sun1 sun2 and that meiotic prophase chromosome movements are abolished, so the telomere-attachment role (redundant with the paralog) is well supported. Accepted. Supporting Evidence: PMID:25412930 Immunolocalization using antibodies against AtSUN1 and AtSUN2 proteins revealed that they were associated with the nuclear envelope during meiotic prophase I PMID:25412930 overlapping functions of SUN1 and SUN2 ensure normal meiotic recombination and synapsis file:ARATH/SUN2/SUN2-uniprot.txt may be involved in telomere attachment to nuclear envelope in the PMID:39013853 Our data confirmed previous results from35 that in the sun1 sun2 double mutant, telomere dynamics are strongly perturbed, and we observed that telomere association with the NE is rare in sun1 sun2, even if not wholly absent PMID:39013853 demonstrating the key role of SUN1 and SUN2 in controlling the meiotic prophase centromere movements file:ARATH/SUN2/SUN2-deep-research-falcon.md Functional redundancy is consequently a central feature of AtSUN2 annotation |
| GO:0090435 protein localization to nuclear envelope | IDA PMID:24667841 Evidence for LINC1-SUN associations at the plant nuclear per... | ACCEPT | Summary: Protein localization to NE: coexpressed SUN proteins recruit and immobilise the lamin-like CRWN1/LINC1 at the NE. Reason: SUN proteins act as the membrane anchor that retains CRWN1 (nucleoplasmic side) at the NE. Note that in planta the NE localization of SUN1/SUN2 does not require CRWN1 and SUN and CRWN1 act independently on nuclear shape (PMID:25759303), so the physiological weight of this anchoring is uncertain, but the process assignment itself is sound. Supporting Evidence: PMID:24667841 AtLINC1 is recruited to the NE by SUN proteins and is immobilised therein PMID:24667841 SUN-dependent NE localisation and immobilisation of LINC1 as well as LINC1-SUN interactions at the NE are strong indicators that SUN proteins are involved in nucleoskeletal anchorage at the plant NE |
| GO:0090435 protein localization to nuclear envelope | IEA GO_REF:0000117 | ACCEPT | Summary: Protein localization to nuclear envelope (ARBA). Reason: Consistent with experimental data. Supporting Evidence: PMID:22270916 The interaction is required for both AtWIP1 and AtRanGAP1 NE localization |
| GO:0090435 protein localization to nuclear envelope | IMP PMID:22270916 Novel plant SUN-KASH bridges are involved in RanGAP anchorin... | ACCEPT | Summary: Protein localization to NE: WIP1 and RanGAP1 NE localization requires SUN proteins. Reason: SUN proteins retain KASH-domain WIPs at the outer nuclear membrane, which in turn anchor RanGAP1; SUN does the anchoring work, so this is a direct role. Supporting Evidence: PMID:22270916 The interaction is required for both AtWIP1 and AtRanGAP1 NE localization PMID:22270916 the GFP-AtWIP1 signal in sun1-KO sun2-KD is predominantly diffuse in the cytoplasm |
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Download this section (compressed HTML)Q: GO:0106094 (nuclear membrane microtubule tethering complex) is used for somatic LINC complexes in animals, but the best-characterized plant SUN-WIP-WIT2-myosin XI-i bridge engages actomyosin. Should GO have a cytoskeleton-neutral LINC complex term (sibling of GO:1990612 Sad1-Kms1 LINC complex) so plant SUN-KASH complexes can be annotated to a complex term?
Suggested experts: GO cellular component editors, plant nuclear envelope biologists
Q: Which KASH partner(s) connect Arabidopsis Cter-SUNs to the meiotic chromosome-movement machinery, and which cytoskeletal motor drives rapid prophase movements (the kinesin PSS1 binds WIP1/WIP2 but its role in movement is untested)?
Suggested experts: plant meiosis researchers
Q: Is SUN-dependent recruitment of CRWN1 (seen on overexpression in tobacco) physiologically relevant, given that SUN and CRWN1 act independently on nuclear shape in Arabidopsis? Would a nuclear matrix anchoring annotation (GO:0090292) be justified for plant Cter-SUNs?
Suggested experts: plant nuclear envelope biologists
Experiment: Telomere FISH combined with NE immunostaining in sun1 sun2 null meiocytes (CRISPR null for the knockdown allele) to test whether telomere attachment to the NE, as opposed to later synapsis, depends on Cter-SUNs.
Type: genetic loss-of-function with cytology
Experiment: Structural or biochemical analysis of Arabidopsis SUN domain trimers bound to WIP/SINE KASH peptides to test whether the plant SUN-KASH interface (including the conserved H/Y pocket and any intermolecular disulfide) mirrors animal SUN2-KASH.
Type: structural biology
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