Abscisic acid-dependent multisite phosphorylation regulates the activity of a transcription activator AREB1.
bZIP-type transcription factors AREBs/ABFs bind an abscisic acid (ABA)-responsive cis-acting element named ABRE and transactivate downstream gene expression in Arabidopsis. Because AREB1 overexpression could not induce downstream gene expression, activation of AREB1 requires ABA-dependent posttranscriptional modification. We confirmed that ABA activated 42-kDa kinase activity, which, in turn, phosphorylated Ser/Thr residues of R-X-X-S/T sites in the conserved regions of AREB1. Amino acid substitutions of R-X-X-S/T sites to Ala suppressed transactivation activity, and multiple substitution of these sites resulted in almost complete suppression of transactivation activity in transient assays. In contrast, substitution of the Ser/Thr residues to Asp resulted in high transactivation activity without exogenous ABA application. A phosphorylated, transcriptionally active form was achieved by substitution of Ser/Thr in all conserved R-X-X-S/T sites to Asp. Transgenic plants overexpressing the phosphorylated active form of AREB1 expressed many ABA-inducible genes, such as RD29B, without ABA treatment. These results indicate that the ABA-dependent multisite phosphorylation of AREB1 regulates its own activation in plants.
Furihata
Takashi
T
Biological Resources Division, Japan International Research Center for Agricultural Sciences, Tsukuba, Ibaraki 305-8686, Japan.
Maruyama
Kyonoshin
K
Fujita
Yasunari
Y
Umezawa
Taishi
T
Yoshida
Riichiro
R
Shinozaki
Kazuo
K
Yamaguchi-Shinozaki
Kazuko
K
D000040:Abscisic Acid / Q000494:pharmacology*; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D017360:Arabidopsis / Q000737:chemistry / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D050976:Basic-Leucine Zipper Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017124:Conserved Sequence; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics; D016415:Sequence Alignment; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D000040:Abscisic Acid; D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D010446:Peptide Fragments; D012333:RNA, Messenger; D015534:Trans-Activators; C508877:At1g45249 protein, Arabidopsis