title: Cochaperonin CPN20 negatively regulates abscisic acid signaling in Arabidopsis.
abstract: Previous study showed that the magnesium-protoporphyrin IX chelatase H subunit (CHLH/ABAR) positively regulates abscisic acid (ABA) signaling. Here, we investigated the functions of a CHLH/ABAR interaction protein, the chloroplast co-chaperonin 20 (CPN20) in ABA signaling in Arabidopsis thaliana. We showed that down-expression of the CPN20 gene increases, but overexpression of the CPN20 gene reduces, ABA sensitivity in the major ABA responses including ABA-induced seed germination inhibition, postgermination growth arrest, promotion of stomatal closure and inhibition of stomatal opening. Genetic evidence supports that CPN20 functions downstream or at the same node of CHLH/ABAR, but upstream of the WRKY40 transcription factor. The other CPN20 interaction partners CPN10 and CPN60 are not involved in ABA signaling. Our findings show that CPN20 functions negatively in the ABAR-WRKY40 coupled ABA signaling independently of its co-chaperonin role, and provide a new insight into the role of co-chaperones in the regulation of plant responses to environmental cues.
authors.affiliation: MOE Systems Biology and Bioinformatics Laboratory, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
authors.forename: Xiao-Feng
authors.initials: XF
authors.lastname: Zhang
authors.forename: Tao
authors.initials: T
authors.lastname: Jiang
authors.forename: Zhen
authors.initials: Z
authors.lastname: Wu
authors.forename: Shu-Yuan
authors.initials: SY
authors.lastname: Du
authors.forename: Yong-Tao
authors.initials: YT
authors.lastname: Yu
authors.forename: Shang-Chuan
authors.initials: SC
authors.lastname: Jiang
authors.forename: Kai
authors.initials: K
authors.lastname: Lu
authors.forename: Xiu-Jing
authors.initials: XJ
authors.lastname: Feng
authors.forename: Xiao-Fang
authors.initials: XF
authors.lastname: Wang
authors.forename: Da-Peng
authors.initials: DP
authors.lastname: Zhang
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D015536:Down-Regulation; D056384:Group I Chaperonins / Q000235:genetics / Q000502:physiology*; D008190:Lyases / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; C478767:Cpn20 protein, Arabidopsis; D000040:Abscisic Acid; D056384:Group I Chaperonins; D008190:Lyases; C086788:magnesium chelatase