Heat stress transcription factor A-1d (HSFA1D) is a class A plant heat shock transcription factor that binds heat shock elements in promoters and contributes to heat-responsive gene expression. Arabidopsis HSFA1D is reported in UniProt as a cytoplasmic and nuclear HSE-binding transcriptional regulator that can interact with HSP90-2, consistent with regulated activation of heat shock factor activity. Its best-characterized properties are sequence-specific DNA-binding transcription factor activity, nuclear/cytoplasmic localization, and a contribution to the heat response; broader roles in light, circadian, thermomorphogenesis, cold, and hormone signaling are less well established.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003700 DNA-binding transcription factor activity | IBA GO_REF:0000033 | ACCEPT | Summary: HSFA1D is a DNA-binding transcription factor that specifically binds heat shock elements (HSE, 5'-nGAAn-3' repeats) in target gene promoters to activate heat stress-responsive genes. The protein contains a conserved winged helix-turn-helix DNA-binding domain. Reason: This annotation accurately reflects the core molecular function of HSFA1D. Extensive evidence demonstrates HSFA1D binds HSEs and activates transcription of heat shock proteins (HSP70, HSP90, small HSPs) and secondary transcription factors (HSFA2, DREB2A). The IBA inference is phylogenetically sound as this function is conserved across plant HSFA1 proteins. Supporting Evidence: file:ARATH/AT1G32330/AT1G32330-deep-research-perplexity.md HSFA1d functions as a master transcription factor that activates a large cohort of downstream genes critical for heat stress survival through recognition and binding to heat shock elements (HSEs) in the promoters of target genes. Heat shock elements are characterized by a consensus DNA sequence comprising inverted repeats of the pentameric motif nGAAn, with HSF trimers optimally binding three repeats of this motif. file:ARATH/AT1G32330/AT1G32330-uniprot.txt FUNCTION: Transcriptional regulator that specifically binds DNA sequence 5'-AGAAnnTTCT-3' known as heat shock promoter elements (HSE). |
| GO:0000978 RNA polymerase II cis-regulatory region sequence-specific DNA binding | IBA GO_REF:0000033 | ACCEPT | Summary: HSFA1D binds to heat shock elements (HSE) in the cis-regulatory regions of RNA polymerase II-transcribed genes, including HSP genes and transcription factor genes. Reason: This annotation correctly captures the sequence-specific DNA binding activity of HSFA1D to cis-regulatory elements (HSEs) in pol II promoters. HSFA1D targets include HSP17, HSP70, HSP90, HSP101, HSFA2, and DREB2A, all transcribed by RNA pol II. The specificity for HSE motifs is well-established. Supporting Evidence: file:ARATH/AT1G32330/AT1G32330-deep-research-perplexity.md The recognition helix (referred to as Ξ±3) of the DBD inserts into the major groove of DNA and mediates the majority of sequence-specific contacts with target DNA through a highly conserved arginine residue that forms bidentate hydrogen bonds with guanine bases in the nGAAn consensus motif. |
| GO:0005634 nucleus | IBA GO_REF:0000033 | ACCEPT | Summary: HSFA1D is annotated as nuclear, consistent with its role as an HSE-binding transcription factor and with UniProt reporting both cytoplasmic and nuclear localization. Reason: Nuclear localization is essential for HSFA1D function as a transcription factor. The protein has a predicted bipartite nuclear localization signal and UniProt reports nucleus as a supported subcellular location. Light-dependent or hormone-dependent localization details are not needed to justify this existing cellular component annotation. Supporting Evidence: file:ARATH/AT1G32330/AT1G32330-deep-research-perplexity.md Upon exposure to heat stress at temperatures typically exceeding 34-37Β°C, HSFA1d rapidly translocates from the cytoplasm to the nucleus through a process that involves dissociation from inhibitory heat shock protein complexes and active nuclear import. Following nuclear entry, HSFA1d undergoes rapid trimerization and binds to heat shock elements in the promoters of target genes to initiate transcriptional activation of the heat shock response. file:ARATH/AT1G32330/AT1G32330-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm. Nucleus. |
| GO:0034605 cellular response to heat | IBA GO_REF:0000033 | ACCEPT | Summary: HSFA1D contributes to the cellular heat stress response as an HSE-binding heat shock transcription factor. The existing IBA annotation is consistent with plant HSF family biology and local evidence for heat-responsive HSFA1D expression and HSP90-regulated heat shock factor activity. Reason: This is an appropriate biological-process annotation for HSFA1D. The gene product has a conserved HSE-binding transcription factor role and the local experimental record includes heat-responsive HSFA1D expression plus HSP90-dependent regulation of heat shock factor activity. More specific claims about light, circadian, cold, or thermomorphogenic outputs are not required for this action. Supporting Evidence: file:ARATH/AT1G32330/AT1G32330-notes.md Triple KO (hsfa1a/b/d): Dramatic thermotolerance defects. Quadruple KO (hsfa1a/b/d/e): Complete loss of acquired thermotolerance. HSFA1D is essential as part of master regulator network. file:ARATH/AT1G32330/AT1G32330-deep-research-perplexity.md HSFA1d improves plant thermotolerance through transcriptional activation of a coordinated program of stress-responsive genes that work together to protect cellular components from thermal damage and maintain cellular homeostasis during heat stress. |
| GO:0003677 DNA binding | IEA GO_REF:0000043 | ACCEPT | Summary: HSFA1D contains a conserved DNA-binding domain (residues 35-129) with winged helix-turn-helix fold. This is the parent term to the more specific GO:0003700 and GO:0000978 annotations. Reason: This is a valid parent molecular function term supported by the presence of the conserved HSF DNA-binding domain. While the more specific terms (GO:0003700, GO:0000978) are more informative, this general DNA binding annotation is correct and can be retained alongside the specific annotations as per standard GO annotation practice. Supporting Evidence: file:ARATH/AT1G32330/AT1G32330-uniprot.txt DNA_BIND 35..129 /evidence="ECO:0000250" |
| GO:0003700 DNA-binding transcription factor activity | IEA GO_REF:0000002 | ACCEPT | Summary: Duplicate of IBA annotation above (line 18). InterPro-based inference agrees with phylogenetic inference. Reason: This is a duplicate annotation of the same GO term with different evidence (IEA from InterPro vs IBA from phylogeny). Both are correct. Duplicate annotations with different evidence codes are acceptable in GO and provide complementary support for the same function. Supporting Evidence: file:ARATH/AT1G32330/AT1G32330-uniprot.txt InterPro IPR000232 HSF_DNA-bd; Pfam PF00447 HSF_DNA-bind |
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: Duplicate of IBA annotation above (line 66). UniProt subcellular location mapping agrees with phylogenetic inference. Reason: This is a duplicate annotation with different evidence (IEA from UniProt keyword mapping vs IBA from phylogeny). Both correctly identify nuclear localization. Duplicate annotations with different evidence codes are acceptable and provide complementary support. Supporting Evidence: file:ARATH/AT1G32330/AT1G32330-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm. Nucleus. |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: HSFA1D localizes to the cytoplasm under non-stress conditions where it is maintained in an inactive state through interactions with HSP70 and HSP90 chaperones. Contains a nuclear export signal (NES) that maintains cytoplasmic retention. Reason: Cytoplasmic localization is well-established for HSFA1D under basal conditions. The protein is sequestered in the cytoplasm through HSP70/HSP90 binding and active export via NES (residues 472-480). This represents the inactive, pre-stress state of the protein before heat-induced nuclear translocation. Supporting Evidence: file:ARATH/AT1G32330/AT1G32330-deep-research-perplexity.md Under normal, non-stress conditions, HSFA1d protein is localized primarily in the cytosol rather than in the nucleus, maintained in an inactive state through interaction with molecular chaperones such as heat shock proteins HSP70 and HSP90. This cytoplasmic sequestration maintains HSFA1d in an inactive state, preventing spurious expression of heat shock proteins in the absence of stress. file:ARATH/AT1G32330/AT1G32330-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm. Nucleus. MOTIF 472..480 /note="Nuclear export signal" |
| GO:0006355 regulation of DNA-templated transcription | IEA GO_REF:0000002 | MODIFY | Summary: HSFA1D regulates transcription by binding to HSE elements and activating RNA pol II-mediated gene expression. This is a general parent term for the specific transcriptional regulation activities. Reason: While technically correct, this term is too general. HSFA1D specifically functions as a positive regulator (activator) of transcription, not a general regulator. The more specific term 'positive regulation of transcription by RNA polymerase II' (GO:0045944) would better capture the actual activity. Proposed replacements: positive regulation of transcription by RNA polymerase II Supporting Evidence: file:ARATH/AT1G32330/AT1G32330-deep-research-perplexity.md HSFA1d functions as a master transcription factor that activates a large cohort of downstream genes critical for heat stress survival through recognition and binding to heat shock elements (HSEs) in the promoters of target genes. |
| GO:0043565 sequence-specific DNA binding | IEA GO_REF:0000002 | ACCEPT | Summary: HSFA1D exhibits sequence-specific DNA binding to HSE motifs (5'-nGAAn-3' repeats). This is a parent term to the more specific GO:0000978 annotation. Reason: This annotation correctly captures the sequence-specific nature of HSFA1D DNA binding. The protein specifically recognizes HSE consensus sequences through its DNA-binding domain. This is a valid parent term that can coexist with more specific annotations (GO:0000978). Supporting Evidence: file:ARATH/AT1G32330/AT1G32330-uniprot.txt FUNCTION: Transcriptional regulator that specifically binds DNA sequence 5'-AGAAnnTTCT-3' known as heat shock promoter elements (HSE). |
| GO:0005634 nucleus | ISM GO_REF:0000122 | ACCEPT | Summary: Third annotation for nuclear localization, based on AtSubP (Arabidopsis Subcellular Proteome) analysis. Agrees with IBA and IEA annotations above. Reason: This is a third independent line of evidence (ISM from AtSubP database) supporting nuclear localization. Multiple annotations with different evidence codes for the same term provide strong support. The protein is experimentally localized to the nucleus under stress conditions. Supporting Evidence: GO_REF:0000122 AtSubP analysis provides computational prediction of subcellular localization based on Arabidopsis-specific training data. |
| GO:0005515 protein binding | IPI PMID:19704818 Cytosolic heat shock protein 90 regulates heat shock transcr... | MODIFY | Summary: HSFA1D interacts with HSP90.2 as demonstrated by protein-protein interaction studies. HSP90 binding maintains HSFA1D in an inactive cytoplasmic state under non-stress conditions. Reason: The IPI evidence from PMID:19704818 supports an interaction with HSP90.2, but the generic 'protein binding' term loses the biologically important identity of the binding partner. Replacing it with Hsp90 protein binding captures the supported HSP90-2 interaction without broadening the annotation to all heat shock proteins or other regulatory partners. Proposed replacements: Hsp90 protein binding Supporting Evidence: PMID:19704818 A. thaliana HSP90.2 interacts with AtHsfA1d, which is one of the constitutively expressed HSFs in A. thaliana. file:ARATH/AT1G32330/AT1G32330-uniprot.txt SUBUNIT: Homotrimer (By similarity). Interacts with HSP90-2 |
| GO:0009408 response to heat | IEP PMID:20229063 Functional characterization of AtHsp90.3 in Saccharomyces ce... | ACCEPT | Summary: HSFA1D transcript expression is induced by heat stress and the protein is essential for heat stress responses. Evidence from PMID:20229063 shows delayed HSFA1D expression when HSP90.3 is overexpressed. Reason: This IEP (Inferred from Expression Pattern) annotation is supported by PMID:20229063 showing that HSFA1D expression is heat-responsive and regulated by HSP90. This is distinct from but complementary to the GO:0034605 (cellular response to heat) annotation - both are valid as they describe different aspects (organism-level response vs cellular response). The experimental evidence clearly demonstrates heat-responsive expression. Supporting Evidence: PMID:20229063 Transcriptional expression of heat stress transcription factors, AtHsfA1d, AtHsfA7a and AtHsfB1, and two Hsps, AtHsp101 and AtHsp17, was delayed by constitutive overexpression of cytosolic AtHsp90.3 under heat stress. file:ARATH/AT1G32330/AT1G32330-notes.md Constitutive expression, Heat-inducible |
| GO:0003700 DNA-binding transcription factor activity | ISS PMID:11118137 Arabidopsis transcription factors: genome-wide comparative a... | ACCEPT | Summary: Third annotation for DNA-binding transcription factor activity, based on sequence similarity (ISS) from genome-wide transcription factor analysis. Agrees with IBA and IEA annotations above. Reason: This is a third independent line of evidence (ISS from PMID:11118137 genome-wide TF analysis) supporting transcription factor activity. PMID:11118137 is the landmark Riechmann et al. 2000 Science paper that classified Arabidopsis transcription factors genome-wide based on DNA-binding domain analysis. Multiple annotations with different evidence codes provide strong convergent support for this core molecular function. Supporting Evidence: PMID:11118137 Arabidopsis transcription factors that belong to families common to all eukaryotes do not share significant similarity with those of the other kingdoms beyond the conserved DNA binding domains. |
Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)