Arabidopsis heat shock factor HsfA1a directly senses heat stress, pH changes, and hydrogen peroxide via the engagement of redox state

• Published in: Plant physiology and biochemistry 2013-03, Vol.64, p.92-98
• Main Authors: Liu, Yanfang, Zhang, Cuixian, Chen, Juan, Guo, Lihong, Li, Xiaolu, Li, Wenpeng, Yu, Zefen, Deng, Jingshi, Zhang, Pengyuan, Zhang, Keqin, Zhang, Lemin
• Format: Article
• Language: English
• Subjects: amino acid deletion; Amino Acids; Arabidopsis; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; Biological and medical sciences; chromatin; DNA; DNA, Plant; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression; Gene Expression Regulation, Plant; genes; Genes, Plant; heat; Heat shock element; Heat shock factor; heat shock proteins; Heat Shock Transcription Factors; heat stress; heat tolerance; Heat-Shock Proteins - genetics; Heat-Shock Proteins - metabolism; Heat-Shock Response - genetics; Hot Temperature; HSP70 Heat-Shock Proteins - genetics; HSP70 Heat-Shock Proteins - metabolism; hydrogen; hydrogen peroxide; Hydrogen Peroxide - pharmacology; Hydrogen-Ion Concentration; in vitro studies; messenger RNA; NADP (coenzyme); Oxidation-Reduction; Oxidative Stress - genetics; Plant physiology and development; Plant Proteins - genetics; Plant Proteins - metabolism; precipitin tests; Promoter Regions, Genetic; Protein Multimerization; Recombinant Proteins - metabolism; Redox state; reducing agents; RNA, Messenger - metabolism; Stress sensing; Stress, Physiological - genetics; transcription (genetics); Transcription Factors - genetics; Transcription Factors - metabolism
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2012.12.013

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. ► Heat, low/high pH, and H2O2 induce Arabidopsis HsfA1a trimerization/DNA-binding. ► The stress-induced HsfA1a DNA-binding parallels its target gene expression. ► The stress-induced HsfA1a trimerization/DNA binding are reversed by reducing agents. ► A deletion mutant of HsfA1a decreases pH-, H2O2-, but not heat-stress sensing.