velB (velvet-like protein B) is a velvet-family regulatory protein and a hub of the fungal developmental regulatory network in Aspergillus nidulans. It participates in two light-regulated complexes: the VelB-VeA-LaeA (velvet) complex formed in the dark, which promotes sexual development and secondary metabolism, and the VosA-VelB complex that controls spore maturation, trehalose biogenesis and repression of cell-wall genes. Through its NF-kB-like velvet domain VelB heterodimerizes with VeA or VosA (VelB alone does not bind the brlA promoter in vitro); it positively regulates sexual sporulation and sterigmatocystin biosynthesis while restraining asexual conidiation, and shuttles between nucleus and cytoplasm.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005634 nucleus | IBA GO_REF:0000033 | ACCEPT | Summary: Nuclear velvet regulator. Reason: VelB is a nuclear DNA-binding regulatory protein (also cytoplasmic); consistent with IDA data. |
| GO:0005992 trehalose biosynthetic process | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: VelB regulates trehalose biogenesis (with VosA). Reason: Regulatory role via the VosA-VelB complex; non-core, non-enzymatic. |
| GO:0030435 sporulation resulting in formation of a cellular spore | IBA GO_REF:0000033 | ACCEPT | Summary: Core process. VelB functions in cellular-spore formation. Reason: VelB is required for proper spore formation/maturation. |
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: Nuclear localization (UniProt mapping). Reason: Consistent with experimental nuclear localization. |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: Cytoplasmic localization (UniProt mapping). Reason: VelB shuttles between cytoplasm and nucleus; consistent with IDA cytoplasm. |
| GO:0005515 protein binding | IPI PMID:24391470 The velvet family of fungal regulators contains a DNA-bindin... | MODIFY | Summary: Protein binding (uninformative MF) reflecting velvet-domain heterodimerization of VelB with VosA, solved crystallographically in this study. Reason: The IPI rests on the VosA-VelB heterodimer, whose crystal structure was determined in this paper; the interaction is a velvet-domain heterodimerization, so protein heterodimerization activity (GO:0046982) is the informative replacement. VelB alone does not bind the brlA promoter in EMSA, so its contribution to DNA binding and transcriptional control is via the heterodimer. Proposed replacements: protein heterodimerization activity Supporting Evidence: PMID:24391470 In order to unveil the molecular basis of the VosA-VelB interaction, we also determined the crystal structure of the VosA1–190-VelB heterodimer PMID:24391470 Overall, these results imply that the homodimers of VosA and VeA may recognize the same promoter regions, while VelB alone at least does not bind the brlA promoter. |
| GO:0048315 conidium formation | IMP PMID:18556559 VelB/VeA/LaeA complex coordinates light signal with fungal d... | ACCEPT | Summary: Core process. VelB regulates conidium formation. Reason: VelB affects conidiation as part of the velvet regulatory network. |
| GO:0043935 sexual sporulation resulting in formation of a cellular spore | IMP PMID:18556559 VelB/VeA/LaeA complex coordinates light signal with fungal d... | ACCEPT | Summary: Core process. VelB promotes sexual sporulation. Reason: VelB (in the velvet complex) promotes sexual development/ascospore formation. Supporting Evidence: PMID:18556559 We identified the heterotrimeric velvet complex VelB/VeA/LaeA connecting light-responding developmental regulation and control of secondary metabolism |
| GO:0045461 sterigmatocystin biosynthetic process | IMP PMID:18556559 VelB/VeA/LaeA complex coordinates light signal with fungal d... | MARK AS OVER ANNOTATED | Summary: Over-annotated: VelB regulates ST biosynthesis, it is not part of the biosynthetic pathway. Reason: VelB influences sterigmatocystin only as a regulator (velvet complex); the precise relationship is captured by GO:0010914 (positive regulation of ST biosynthesis). Proposed replacements: positive regulation of sterigmatocystin biosynthetic process |
| GO:0071482 cellular response to light stimulus | IMP PMID:18556559 VelB/VeA/LaeA complex coordinates light signal with fungal d... | KEEP AS NON CORE | Summary: VelB participates in the light response (velvet complex is light-regulated). Reason: The velvet complex couples light signalling to development; VelB's role in cellular response to light is real but non-core. |
| GO:0005634 nucleus | IDA PMID:21152013 LaeA control of velvet family regulatory proteins for light-... | ACCEPT | Summary: Nuclear localization (direct). Reason: Direct assay; consistent with velvet-complex nuclear function. Supporting Evidence: PMID:21152013 The VosA-VelB YFP signal colocalized predominantly to the nuclear RFP signal, indicating that the VosA-VelB complex is formed in the nucleus |
| GO:0005737 cytoplasm | IDA PMID:21152013 LaeA control of velvet family regulatory proteins for light-... | ACCEPT | Summary: Cytoplasmic localization (direct). Reason: Direct assay; VelB is partly cytoplasmic. Supporting Evidence: PMID:21152013 In contrast, we found the combined signal of N-YFP::VelB and C-YFP::VelB in vivo in the cytoplasm as well as in the nucleus |
| GO:0005992 trehalose biosynthetic process | IMP PMID:21152013 LaeA control of velvet family regulatory proteins for light-... | KEEP AS NON CORE | Summary: VelB regulates trehalose biosynthesis (direct, regulatory). Reason: Regulatory role via VosA-VelB; non-core. |
| GO:0005634 nucleus | IDA PMID:18556559 VelB/VeA/LaeA complex coordinates light signal with fungal d... | ACCEPT | Summary: Nuclear localization (direct). Reason: Direct assay from the velvet-complex study. |
| GO:0005737 cytoplasm | IDA PMID:18556559 VelB/VeA/LaeA complex coordinates light signal with fungal d... | ACCEPT | Summary: Cytoplasmic localization (direct). Reason: Direct assay; consistent with nucleocytoplasmic distribution. |
| GO:0010914 positive regulation of sterigmatocystin biosynthetic process | IMP PMID:18556559 VelB/VeA/LaeA complex coordinates light signal with fungal d... | KEEP AS NON CORE | Summary: VelB positively regulates ST biosynthesis (real, non-core SM role). Reason: As part of the velvet complex VelB promotes sterigmatocystin biosynthesis; a genuine but pleiotropic non-core role. Supporting Evidence: PMID:18556559 We identified the heterotrimeric velvet complex VelB/VeA/LaeA connecting light-responding developmental regulation and control of secondary metabolism |
| GO:0043941 positive regulation of sexual sporulation resulting in formation of a cellular spore | IMP PMID:18556559 VelB/VeA/LaeA complex coordinates light signal with fungal d... | ACCEPT | Summary: Core process. VelB positively regulates sexual sporulation. Reason: VelB promotes sexual sporulation (ascospore formation) via the velvet complex. Supporting Evidence: PMID:18556559 VeA, which is primarily expressed in the dark, physically interacts with VelB, which is expressed during sexual development |
| GO:0075308 negative regulation of conidium formation | IMP PMID:18556559 VelB/VeA/LaeA complex coordinates light signal with fungal d... | ACCEPT | Summary: Core process. VelB negatively regulates conidium formation. Reason: VelB restrains asexual conidiation while promoting sexual development, balancing developmental fate. |
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