The plant hormone abscisic acid (ABA) regulates many aspects of plant development and stress response. The ubiquitin/26S proteasome pathway plays a very important role in hormone signaling. Since the identification of ABA receptor, considerable progress has been made in understanding ABA signaling pathway. However, the mechanism of endoplasmic membrane (ER) in mediating the signal from ABA perception to transcription factor remains unknown.
Early studies of XIE Qi’s lab in Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, isolated a RING type ubiquitin ligase SDIR1 (SALT- AND DROUGHT-INDUCED REALLY INTERESTING NEW GENE FINGER1). SDIR1 enhances ABA signal by increasing the expression of a serious of bZIP transcription factor, and regulates tolerant ability of plant to drought and salt stress (Zhang et al., 2007, Plant Cell). After that, Xie’s lab attempted to make a further study of SDIR1’s function by isolation its direct substrate.
Using yeast two-hybrid screening, they identified SDIRIP1 (SDIR1-INTERACTING PROTEIN1) as a substrate of SDIR1. Cell biology assays indicated that SDIR1 is localized on ER membrane, and the C-terminus of SDIR1, which includes RING domain, faces the cytoplasm; SDIRIP1 is localized to the chloroplast, cell periphery and nucleus. Using biochemistry, cell biology and genetic approaches, they demonstrated that the SDIRIP1 negatively regulates ABA signaling by suppress the expression of ABI5, and C-terminus of SDIR1 can interact with SDIRIP1, and promote SDIRIP1’s degradation through ubiquitin/26Sproteasome pathway.
This study uncovered the function of SDIR/SDIRIP1 in ABA pathway, and provided some clues on the study of communication signals among different organelles.
This work has been online published in
the Plant Cell online Early Edition on January 26, 2015
(DOI:10.1105/tpc.114.134163), with the assistant professor ZHANG Huawei as the first author. This research was supported by 973 Program Grant from the National Basic Research Program of China and Grant from the National Science Foundation of China.
AUTHOR CONTACT:
XIE Qi, Ph.D.
Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.
E-mail: qxie@genetics.ac.cn
