BPH1, a novel substrate receptor of CRL3, plays a repressive role in ABA signal transduction |
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| Authors: | Og-Geum Woo Soon-Hee Kim Seok Keun Cho Sang-Hoon Kim Han Nim Lee Taijoon Chung Seong Wook Yang Jae-Hoon Lee |
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| Institution: | 1.Department of Biology Education,Pusan National University,Busan,South Korea;2.Department of Integrated Biological Science,Pusan National University,Busan,South Korea;3.Department of Systems Biology, College of Life Science and Biotechnology,Yonsei University,Seoul,South Korea;4.Department of Biological Sciences,Pusan National University,Busan,South Korea;5.Section of Plant Biochemistry, Department of Plant and Environmental Sciences, Faculty of Sciences,University of Copenhagen,Frederiksberg C,Denmark |
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| Abstract: | Key messageBPH1 acts as a substrate receptor of CRL3 complex and negatively regulates ABA-mediated cellular responses. The study on its function provides information that helps further understand the relationship between ABA signaling and UPS.AbstractAbscisic acid (ABA) plays a crucial role in a variety of cellular processes, including seed dormancy, inhibition of seedling growth, and drought resistance in plants. Cullin3-RING E3 ligase (CRL3) complex is a type of multi-subunit E3 ligase, and BTB/POZ protein, a component of CRL3 complex, functions as a receptor to determine a specific substrate. To elucidate the CRL3 complex that participates in ABA-mediated cellular processes, we first investigated ABA-inducible BTB/POZ genes based on data from the AtGenExpress Visualization Tool (AVT). We then isolated an ABA-inducible gene encoding a potential CRL3 substrate receptor in Arabidopsis, BPH1 (BTB/POZ protein hypersensitive to ABA 1). The isolate gene has a BTB/POZ domain and a NPH3 domain within its N-terminal and C-terminal region, respectively. Yeast two-hybrid and co-immunoprecipitation assays showed that BPH1 physically interacted with cullin3a, a scaffold protein of CRL3, suggesting that it functions as an Arabidopsis CRL3 substrate receptor. The functional mutation of BPH1 caused delayed seed germination in response to ABA and enhanced sensitivity by NaCl and mannitol treatments as ABA-related stresses. Moreover, bph1 mutants exhibited enhanced stomatal closure under ABA application and reduced water loss when compared with wild-type, implying their enhanced tolerance to drought stress. Based on the information from microarray/AVT data and expression analysis of various ABA-inducible genes between wild-type and bph1 plants following ABA treatments, we concluded loss of BPH1 resulted in hyper-induction of a large portion of ABA-inducible genes in response to ABA. Taken together, these results show that BPH1 is negatively involved in ABA-mediated cellular events. |
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