title: Arabidopsis heat shock factor HsfA1a directly senses heat stress, pH changes, and hydrogen peroxide via the engagement of redox state.
abstract: Arabidopsis heat shock factor HsfA1a is present in a latent, monomeric state under normal conditions; its activation involves heat stress-induced trimerization, binding to heat shock element in target promoters, and the acquisition of transcriptional competence. HsfA1a is an important regulator for heat stress-induced gene expression and thermotolerance. However, it is not clear whether HsfA1a is directly activated by stress and the mechanisms of the stress signaling are poorly understood. We analyzed HsfA1a activation by trimerization and DNA-binding assays in vitro and in vivo in response to heat stress, low/high pH, and hydrogen peroxide treatments. Our results show that purified recombinant HsfA1a was activated by these stress treatments in vitro. The same treatments also induced the binding to HSP18.2 and HSP70 promoters as examined by chromatin immunoprecipitation, and the HsfA1a DNA binding paralleled the mRNA expression of its target genes induced by different stresses. Stress-induced DNA-binding could be reversed, both in vitro and in vivo, by subsequent incubation with reducing agents (DTT, NADPH). These data suggest that HsfA1a can directly sense stress and become activated, and this process is dependent on the redox state. An N-terminal deletion of the amino acid residues from 48 to 74 negatively affected pH- and hydrogen peroxide-, but not heat-stress sensing.
authors: Laboratory for Conservation and Utilization of Bio-resources, Yunnan University, Kunming 650091, China.
authors: Yanfang
authors: Y
authors: Liu
authors: Cuixian
authors: C
authors: Zhang
authors: Juan
authors: J
authors: Chen
authors: Lihong
authors: L
authors: Guo
authors: Xiaolu
authors: X
authors: Li
authors: Wenpeng
authors: W
authors: Li
authors: Zefen
authors: Z
authors: Yu
authors: Jingshi
authors: J
authors: Deng
authors: Pengyuan
authors: P
authors: Zhang
authors: Keqin
authors: K
authors: Zhang
authors: Lemin
authors: L
authors: Zhang
mesh_terms: D000596:Amino Acids; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D018744:DNA, Plant; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D018869:Heat-Shock Response / Q000235:genetics*; D006358:Hot Temperature; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D055503:Protein Multimerization; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013312:Stress, Physiological / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D000596:Amino Acids; D029681:Arabidopsis Proteins; D018744:DNA, Plant; D004268:DNA-Binding Proteins; C446287:HSP18.2 protein, Arabidopsis; D018840:HSP70 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D010940:Plant Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014157:Transcription Factors; D006861:Hydrogen Peroxide