SOS2-LIKE PROTEIN KINASE5, an SNF1-RELATED PROTEIN KINASE3-Type Protein Kinase, Is Important for Abscisic Acid Responses in Arabidopsis through Phosphorylation of ABSCISIC ACID-INSENSITIVE51[OPEN]

A salt sensitive-like protein kinase and phosphorylation of its unique target affect ABA inhibition of seed germination. Abscisic acid ( ABA ) plays an essential role in seed germination. In this study, we demonstrate that one SNF1-RELATED PROTEIN KINASE3-type protein kinase, SOS2-LIKE PROTEIN KINAS...

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Published in:Plant physiology (Bethesda) 2015-04, Vol.168 (2), p.659-676
Main Authors: Zhou, Xiaona, Hao, Hongmei, Zhang, Yuguo, Bai, Yili, Zhu, Wenbo, Qin, Yunxia, Yuan, Feifei, Zhao, Feiyi, Wang, Mengyao, Hu, Jingjiang, Xu, Hong, Guo, Aiguang, Zhao, Huixian, Zhao, Yang, Cao, Cuiling, Yang, Yongqing, Schumaker, Karen S., Guo, Yan, Xie, Chang Gen
Format: Article
Language:English
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Summary:A salt sensitive-like protein kinase and phosphorylation of its unique target affect ABA inhibition of seed germination. Abscisic acid ( ABA ) plays an essential role in seed germination. In this study, we demonstrate that one SNF1-RELATED PROTEIN KINASE3-type protein kinase, SOS2-LIKE PROTEIN KINASE5 (PKS5), is involved in ABA signal transduction via the phosphorylation of an interacting protein, ABSCISIC ACID-INSENSITIVE5 (ABI5). We found that pks5-3 and pks5-4 , two previously identified PKS5 superactive kinase mutants with point mutations in the PKS5 FISL/NAF (a conserved peptide that is necessary for interaction with SOS3 or SOS3-LIKE CALCIUM BINDING PROTEINs) motif and the kinase domain, respectively, are hypersensitive to ABA during seed germination. PKS5 was found to interact with ABI5 in yeast ( Saccharomyces cerevisiae ), and this interaction was further confirmed in planta using bimolecular fluorescence complementation. Genetic studies revealed that ABI5 is epistatic to PKS5 . PKS5 phosphorylates a serine (Ser) residue at position 42 in ABI5 and regulates ABA -responsive gene expression. This phosphorylation was induced by ABA in vivo and transactivated ABI5. Expression of ABI5, in which Ser-42 was mutated to alanine, could not fully rescue the ABA -insensitive phenotypes of the abi5-8 and pks5-4abi5-8 mutants. In contrast, mutating Ser-42 to aspartate rescued the ABA insensitivity of these mutants. These data demonstrate that PKS5-mediated phosphorylation of ABI5 at Ser-42 is critical for the ABA regulation of seed germination and gene expression in Arabidopsis ( Arabidopsis thaliana ).
ISSN:0032-0889
1532-2548
DOI:10.1104/pp.114.255455