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HSFA2 and HSFA3 binding after heat acclimation [DAP-seq]

ABSTRACT: Transcriptional regulation is a key aspect of environmental stress responses. Heat stress (HS) induces transcriptional memory that allows plants to respond more efficiently to a recurrent HS. In light of more frequent temperature extremes due to climate change, improving heat tolerance in crops is an important breeding goal. However, not all HS-inducible genes show sustained induction/transcriptional memory and it is unclear what distinguishes memory and non-memory genes. To address this issue and understand the (epi-) genome architecture in transcriptional memory after HS, we investigated genome-wide target genes of the two key memory heat shock transcription factors, HSFA2 and HSFA3. We determined the binding kinetics of these factors to their target genes and asked whether genes that show sustained induction of transcription carry specific features that allow prediction and potentially engineering of memory gene behaviour. HSFA2 and HSFA3 show near identical binding patterns. In vitro binding strength as determined by DAP-seq analysis correlates strongly with in vivo binding strength, confirming the importance of sequence features. However, no single distinctive sequence motif appears to be required for memory behaviour. Instead, HS memory genes are characterized by a combination of features: low expression levels in the absence of HS, chromatin environment and an enrichment of H3K4 methylation after HS. Our findings are confirmed by an orthogonal transcriptomic data set using both de novo clustering and an established definition of memory genes. In summary, our findings provide an integrated view of HSF-dependent transcriptional memory and shed light on its sequence and chromatin determinants. They will contribute to the prediction and engineering of genes with transcriptional memory.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE192407 | GEO | 2023/05/07

REPOSITORIES: GEO

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Project description:The expression of heat-shock proteins (Hsps) induced by a non-lethal heat treatment confers acquired thermotolerance (AT) to organisms against a subsequent challenge of otherwise lethal temperature. After stress signal lifted, AT gradually decayed with the decline of Hsps during recovery period. The duration of AT may be critical for sessile organisms, such as plants, to survive repeated heat stress in the environment. To identify heat-induced genes involved in duration of AT, we took a reverse-genetics approach by screening for Arabidopsis T-DNA insertion mutants that show decreased thermotolerance after a long recovery at non-stress condition following a conditioning treatment. Among the tested mutants corresponding to 47 genes, only the HsfA2 knockout mutant showed significant phenotype. The mutant plants were more sensitive to severe heat stress than the wild type after long but not short recovery following a pretreatment at 37oC, which can be complemented by introducing a wild-type copy of the gene. Quantitative hypocotyl elongation assay also revealed that AT decayed faster in the absence of HsfA2. Significant decline of the transcript levels of several highly heat-induced genes was observed in the HsfA2 knockout plants after a 4-h recovery or after 2 h of prolonged heat stress. Immunoblot anlysis showed that Hsa32 and class I small Hsp were lower in the mutant than in the wild type after a long recovery. Our results suggest that HsfA2 as a heat-induced transactivator sustains the post-stress expression of Hsp genes and extends the duration of AT in Arabidopsis. Experiment Overall Design: Total RNA was isolated from the seedlings of 5-d old wild-type and HsfA2 knockout mutant seedlings (a pool of about 100 plants per treatment in duplicates) harvested immediately after heat shock treatment. In this experiment, total 12 chips were used, 1 each for 2 biological replicates of the control and HS-treated samples for the wild type and mutant plants.

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HSFA2 and HSFA3 binding after heat acclimation [DAP-seq]

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