title: The Transcriptional Cascade in the Heat Stress Response of Arabidopsis Is Strictly Regulated at the Level of Transcription Factor Expression.
abstract: Group A1 heat shock transcription factors (HsfA1s) are the master regulators of the heat stress response (HSR) in plants. Upon heat shock, HsfA1s trigger a transcriptional cascade that is composed of many transcription factors. Despite the importance of HsfA1s and their downstream transcriptional cascade in the acquisition of thermotolerance in plants, the molecular basis of their activation remains poorly understood. Here, domain analysis of HsfA1d, one of several HsfA1s in Arabidopsis thaliana, demonstrated that the central region of HsfA1d is a key regulatory domain that represses HsfA1d transactivation activity through interaction with HEAT SHOCK PROTEIN70 (HSP70) and HSP90. We designated this region as the temperature-dependent repression (TDR) domain. We found that HSP70 dissociates from HsfA1d in response to heat shock and that the dissociation is likely regulated by an as yet unknown activation mechanism, such as HsfA1d phosphorylation. Overexpression of constitutively active HsfA1d that lacked the TDR domain induced expression of heat shock proteins in the absence of heat stress, thereby conferring potent thermotolerance on the overexpressors. However, transcriptome analysis of the overexpressors demonstrated that the constitutively active HsfA1d could not trigger the complete transcriptional cascade under normal conditions, thereby indicating that other factors are necessary to fully induce the HSR. These complex regulatory mechanisms related to the transcriptional cascade may enable plants to respond resiliently to various heat stress conditions.
authors.affiliation: Graduate School of Agricultural and Life Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Naohiko
authors.identifier: http://orcid.org/0000-0002-6762-5975
authors.initials: N
authors.lastname: Ohama
authors.affiliation: Graduate School of Agricultural and Life Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Kusakabe
authors.affiliation: Graduate School of Agricultural and Life Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Junya
authors.initials: J
authors.lastname: Mizoi
authors.affiliation: Graduate School of Agricultural and Life Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Huimei
authors.identifier: http://orcid.org/0000-0002-1082-2118
authors.initials: H
authors.lastname: Zhao
authors.affiliation: Graduate School of Agricultural and Life Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kidokoro
authors.affiliation: Graduate School of Agricultural and Life Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Koizumi
authors.affiliation: RIKEN Center for Sustainable Resource Science, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan.
authors.forename: Fuminori
authors.initials: F
authors.lastname: Takahashi
authors.affiliation: Biotechnology Research Center, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Ishida
authors.affiliation: Biotechnology Research Center, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Shuichi
authors.initials: S
authors.lastname: Yanagisawa
authors.affiliation: RIKEN Center for Sustainable Resource Science, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Shinozaki
authors.affiliation: Graduate School of Agricultural and Life Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan akys@mail.ecc.u-tokyo.ac.jp.
authors.forename: Kazuko
authors.identifier: http://orcid.org/0000-0002-0249-8258
authors.initials: K
authors.lastname: Yamaguchi-Shinozaki
mesh_terms: D020816:Amino Acid Motifs; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D002853:Chromatography, Liquid; D017124:Conserved Sequence; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018869:Heat-Shock Response / Q000235:genetics*; D008954:Models, Biological; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011523:Protoplasts / Q000378:metabolism; D017384:Sequence Deletion / Q000235:genetics; D013329:Structure-Activity Relationship; D053719:Tandem Mass Spectrometry; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic; D059467:Transcriptome / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D014157:Transcription Factors