2009年5月15日，北京生命科學研究所郭巖實驗室在The Plant Cell雜誌在線發表題為「Phosphorylation of SOS3-LIKE CALCIUM BINDING PROTEIN8 by SOS2 Protein Kinase Stabilizes Their Protein Complex and Regulates Salt Tolerance in Arabidopsis」的文章，該文章報導了SCaBP8在體內被SOS2磷酸化在調節植物耐鹽性中的作用。
調節細胞中的離子平衡對植物的生長發育是至關重要的。研究表明SOS信號途徑在調節植物鈉鉀平衡和耐鹽性中起關鍵作用。鈣結合蛋白SOS3和SCaBP8通過激活蛋白激酶SOS2保護擬南芥免受外界的鹽脅迫。SOS3主要作用在根部，而SCaBP8主要作用在地上部分。由於它們異位表達後並不能相互恢復各自的表型，於是推測它們有著獨特的調節機制。在這個研究中我們發現SOS2不能磷酸化SOS3，但卻能夠磷酸化SCaBP8。該磷酸化反應發生在膜上，並受鹽誘導。它穩定了SCaBP8-SOS2的相互作用，並增強質膜鈉氫轉運蛋白的活性。當SCaBP8蛋白絲氨酸-237突變成丙氨酸時，SOS2不再能磷酸化SCaBP8。這個突變的蛋白也就不能夠完全恢復scabp8鹽敏感表型。而絲氨酸-237突變成能夠模擬磷酸化的天冬氨酸則能夠完全恢復scabp8的表型。這些結果表明SCaBP8被SOS2磷酸化是SOS信號途徑調節擬南芥耐鹽機制的重要一環。
該文章的第一作者為林慧馨，通訊作者為郭巖博士，該項研究由科技部863項目和北京市科委資助。（生物谷Bioon.com）
生物谷推薦原始出處：
Plant Cell May 15, 2009; 10.1105/tpc.109.066217
Phosphorylation of SOS3-LIKE CALCIUM BINDING PROTEIN8 by SOS2 Protein Kinase Stabilizes Their Protein Complex and Regulates Salt Tolerance in Arabidopsis
Huixin Lin 1, Yongqing Yang 1, Ruidang Quan 1, Imelda Mendoza 2, Yisheng Wu 1, Wenming Du 1, Shuangshuang Zhao 1, Karen S. Schumaker 3, José M. Pardo 2, and Yan Guo 1*
1 National Institute of Biological Sciences, Beijing, Zhongguancun Life Science Park, Beijing 102206, P.R. China
2 Instituto de Recursos Naturales y Agrobiología, Consejo Superior de Investigaciones Científicas, Sevilla 41012, Spain
3 Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721
The Salt Overly Sensitive (SOS) pathway plays an important role in the regulation of Na+/K+ ion homeostasis and salt tolerance in Arabidopsis thaliana. Previously, we reported that the calcium binding proteins SOS3 and SOS3-LIKE CALCIUM BINDING PROTEIN8 (SCaBP8) nonredundantly activate the protein kinase SOS2. Here, we show that SOS2 phosphorylates SCaBP8 at its C terminus but does not phosphorylate SOS3. In vitro, SOS2 phosphorylation of SCaBP8 was enhanced by the bimolecular interaction of SOS2 and SCaBP8 and did not require calcium ions. In vivo, this phosphorylation was induced by salt stress, occurred at the membrane, stabilized the SCaBP8-SOS2 interaction, and enhanced plasma membrane Na+/H+ exchange activity. When a Ser at position 237 in the SCaBP8 protein (the SOS2 phosphorylation target) was mutated to Ala, SCaBP8 was no longer phosphorylated by SOS2 and the mutant protein could not fully rescue the salt-sensitive phenotype of the scabp8 mutant. By contrast, when Ser-237 was mutated to Asp to mimic the charge of a phosphorylated Ser residue, the mutant protein rescued the scabp8 salt sensitivity. These data demonstrate that calcium sensor phosphorylation is a critical component of SOS pathway regulation of salt tolerance in Arabidopsis.