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AtAIRP2 E3 ligase affects ABA and high-salinity responses by stimulating its ATP1/SDIRIP1 substrate turnover

 Tae Rin Oh  ;  Jong Hum Kim  ;  Seok Keun Cho  ;  Moon Young Ryu  ;  Seong Wook Yang  ;  Woo Taek Kim 
 Plant Physiology, Vol.174(4) : 2515-2531, 2017 
Journal Title
 Plant Physiology 
Issue Date
Abscisic Acid/pharmacology* ; Arabidopsis/drug effects ; Arabidopsis/genetics ; Arabidopsis/metabolism* ; Arabidopsis Proteins/metabolism* ; Cell Compartmentation ; Cytosol/drug effects ; Cytosol/metabolism ; Down-Regulation/genetics ; Epistasis, Genetic/drug effects ; Genetic Complementation Test ; Germination/drug effects ; Models, Biological ; Molecular Chaperones/metabolism ; Plant Epidermis/cytology ; Proteasome Endopeptidase Complex/metabolism ; Protein Binding/drug effects ; Protein Subunits/metabolism ; Proton-Translocating ATPases/metabolism* ; Salinity* ; Seeds/drug effects ; Seeds/growth & development ; Subcellular Fractions/metabolism ; Substrate Specificity/drug effects ; Tobacco/cytology
AtAIRP2 is a cytosolic RING-type E3 ubiquitin ligase that positively regulates an abscisic acid (ABA) response in Arabidopsis (Arabidopsis thaliana). Yeast two-hybrid screening using AtAIRP2 as bait identified ATP1 (AtAIRP2 Target Protein1) as a substrate of AtAIRP2. ATP1 was found to be identical to SDIRIP1, which was reported recently to be a negative factor in ABA signaling and a target protein of the RING E3 ligase SDIR1. Accordingly, ATP1 was renamed ATP1/SDIRIP1. A specific interaction between AtAIRP2 and ATP1/SDIRIP1 and ubiquitination of ATP1/SDIRIP1 by AtAIRP2 were demonstrated in vitro and in planta. The turnover of ATP1/SDIRIP1 was regulated by AtAIRP2 in cell-free degradation and protoplast cotransfection assays. The ABA-mediated germination assay of 35S:ATP1/SDIRIP1-RNAi/atairp2 double mutant progeny revealed that ATP1/SDIRIP1 acts downstream of AtAIRP2. AtAIRP2 and SDIR1 reciprocally complemented the ABA- and salt-insensitive germination phenotypes of sdir1 and atairp2 mutants, respectively, indicating their combinatory roles in seed germination. Subcellular localization and bimolecular fluorescence complementation experiments in the presence of MG132, a 26S proteasome inhibitor, showed that AtAIRP2 and ATP1/SDIRIP1 were colocalized to the cytosolic spherical body, which lies in close proximity to the nucleus, in tobacco (Nicotiana benthamiana) leaf cells. The 26S proteasome subunits RPN12a and RPT1 and the molecular chaperones HSP70 and HSP101 were colocalized to these discrete punctae-like structures. These results raised the possibility that AtAIRP2 and ATP1/SDIRIP1 interact in the cytosolic spherical compartment. Collectively, our data suggest that the down-regulation of ATP1/SDIRIP1 by AtAIRP2 and SDIR1 RING E3 ubiquitin ligases is critical for ABA and high-salinity responses during germination in Arabidopsis.
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1. Journal Papers (연구논문) > 1. College of Medicine (의과대학) > Dept. of Pharmacology (약리학교실)
Yonsei Authors
유문영(Ryu, Moon Young)
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