title: The Mg-chelatase H subunit is an abscisic acid receptor.
abstract: Abscisic acid (ABA) is a vital phytohormone that regulates mainly stomatal aperture and seed development, but ABA receptors involved in these processes have yet to be determined. We previously identified from broad bean an ABA-binding protein (ABAR) potentially involved in stomatal signalling, the gene for which encodes the H subunit of Mg-chelatase (CHLH), which is a key component in both chlorophyll biosynthesis and plastid-to-nucleus signalling. Here we show that Arabidopsis ABAR/CHLH specifically binds ABA, and mediates ABA signalling as a positive regulator in seed germination, post-germination growth and stomatal movement, showing that ABAR/CHLH is an ABA receptor. We show also that ABAR/CHLH is a ubiquitous protein expressed in both green and non-green tissues, indicating that it might be able to perceive the ABA signal at the whole-plant level.
authors.affiliation: China State Key Laboratory of Plant Physiology and Biochemistry, China Agricultural University, 100094 Beijing, China.
authors.forename: Yuan-Yue
authors.initials: YY
authors.lastname: Shen
authors.forename: Xiao-Fang
authors.initials: XF
authors.lastname: Wang
authors.forename: Fu-Qing
authors.initials: FQ
authors.lastname: Wu
authors.forename: Shu-Yuan
authors.initials: SY
authors.lastname: Du
authors.forename: Zheng
authors.initials: Z
authors.lastname: Cao
authors.forename: Yi
authors.initials: Y
authors.lastname: Shang
authors.forename: Xiu-Ling
authors.initials: XL
authors.lastname: Wang
authors.forename: Chang-Cao
authors.initials: CC
authors.lastname: Peng
authors.forename: Xiang-Chun
authors.initials: XC
authors.lastname: Yu
authors.forename: Sai-Yong
authors.initials: SY
authors.lastname: Zhu
authors.forename: Ren-Chun
authors.initials: RC
authors.lastname: Fan
authors.forename: Yan-Hong
authors.initials: YH
authors.lastname: Xu
authors.forename: Da-Peng
authors.initials: DP
authors.lastname: Zhang
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D008190:Lyases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified; D011485:Protein Binding; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013379:Substrate Specificity
chemical_list: D029681:Arabidopsis Proteins; D021122:Protein Subunits; D000040:Abscisic Acid; D008190:Lyases; C086788:magnesium chelatase