The Mg-chelatase H subunit of Arabidopsis antagonizes a group of WRKY transcription repressors to relieve ABA-responsive genes of inhibition.
The phytohormone abscisic acid (ABA) plays a vital role in plant development and response to environmental challenges, but the complex networks of ABA signaling pathways are poorly understood. We previously reported that a chloroplast protein, the magnesium-protoporphyrin IX chelatase H subunit (CHLH/ABAR), functions as a receptor for ABA in Arabidopsis thaliana. Here, we report that ABAR spans the chloroplast envelope and that the cytosolic C terminus of ABAR interacts with a group of WRKY transcription factors (WRKY40, WRKY18, and WRKY60) that function as negative regulators of ABA signaling in seed germination and postgermination growth. WRKY40, a central negative regulator, inhibits expression of ABA-responsive genes, such as ABI5. In response to a high level of ABA signal that recruits WRKY40 from the nucleus to the cytosol and promotes ABAR-WRKY40 interaction, ABAR relieves the ABI5 gene of inhibition by repressing WRKY40 expression. These findings describe a unique ABA signaling pathway from the early signaling events to downstream gene expression.
Shang
Yi
Y
Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China.
Yan
Lu
L
Liu
Zhi-Qiang
ZQ
Cao
Zheng
Z
Mei
Chao
C
Xin
Qi
Q
Wu
Fu-Qing
FQ
Wang
Xiao-Fang
XF
Du
Shu-Yuan
SY
Jiang
Tao
T
Zhang
Xiao-Feng
XF
Zhao
Rui
R
Sun
Hai-Li
HL
Liu
Rui
R
Yu
Yong-Tao
YT
Zhang
Da-Peng
DP
D000040:Abscisic Acid / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018525:Germination; D008190:Lyases / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics; D011401:Promoter Regions, Genetic; D018749:RNA, Plant / Q000235:genetics; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D008565:Membrane Proteins; D010937:Plant Growth Regulators; D018749:RNA, Plant; D014157:Transcription Factors; C512070:WRKY40 protein, Arabidopsis; D000040:Abscisic Acid; D008190:Lyases; C086788:magnesium chelatase