Wang Chuang, Yue Wenhao, Ying Yinghui, Wang Shoudong, Secco David, Liu Yu, Whelan James, Tyerman Stephen D, Shou Huixia
State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China (C.W., W.Y., Y.Y., S.W., Y.L., H.S.);Australian Research Council Centre of Excellence in Plant Energy Biology, Department of Plant Science, School of Agriculture Food and Wine, University of Adelaide, Glen Osmond, South Australia 5064, Australia (C.W., S.D.T.);Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Perth, Western Australia 6009, Australia (D.S.); andDepartment of Animal, Plant, and Soil Science, Australian Research Council Centre of Excellence in Plant Energy Biology, School of Life Science, La Trobe University, Melbourne, Victoria 3086, Australia (J.W.).
State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China (C.W., W.Y., Y.Y., S.W., Y.L., H.S.);Australian Research Council Centre of Excellence in Plant Energy Biology, Department of Plant Science, School of Agriculture Food and Wine, University of Adelaide, Glen Osmond, South Australia 5064, Australia (C.W., S.D.T.);Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Perth, Western Australia 6009, Australia (D.S.); andDepartment of Animal, Plant, and Soil Science, Australian Research Council Centre of Excellence in Plant Energy Biology, School of Life Science, La Trobe University, Melbourne, Victoria 3086, Australia (J.W.)
Plant Physiol. 2015 Dec;169(4):2822-31. doi: 10.1104/pp.15.01005. Epub 2015 Sep 30.
To maintain a stable cytosol phosphate (Pi) concentration, plant cells store Pi in their vacuoles. When the Pi concentration in the cytosol decreases, Pi is exported from the vacuole into the cytosol. This export is mediated by Pi transporters on the tonoplast. In this study, we demonstrate that SYG1, PHO81, and XPR1 (SPX)-Major Facility Superfamily (MFS) proteins have a similar structure with yeast (Saccharomyces cerevisiae) low-affinity Pi transporters Phosphatase87 (PHO87), PHO90, and PHO91. OsSPX-MFS1, OsSPX-MFS2, and OsSPX-MFS3 all localized on the tonoplast of rice (Oryza sativa) protoplasts, even in the absence of the SPX domain. At high external Pi concentration, OsSPX-MFS3 could partially complement the yeast mutant strain EY917 under pH 5.5, which lacks all five Pi transporters present in yeast. In oocytes, OsSPX-MFS3 was shown to facilitate Pi influx or efflux depending on the external pH and Pi concentrations. In contrast to tonoplast localization in plants cells, OsSPX-MFS3 was localized to the plasma membrane when expressed in both yeast and oocytes. Overexpression of OsSPX-MFS3 results in decreased Pi concentration in the vacuole of rice tissues. We conclude that OsSPX-MFS3 is a low-affinity Pi transporter that mediates Pi efflux from the vacuole into cytosol and is coupled to proton movement.
为维持稳定的胞质溶胶磷酸盐（Pi）浓度，植物细胞将Pi储存在液泡中。当胞质溶胶中的Pi浓度降低时，Pi从液泡输出到胞质溶胶中。这种输出由液泡膜上的Pi转运蛋白介导。在本研究中，我们证明SYG1、PHO81和XPR1（SPX）-主要易化子超家族（MFS）蛋白与酵母（酿酒酵母）低亲和力Pi转运蛋白Phosphatase87（PHO87）、PHO90和PHO91具有相似结构。OsSPX-MFS1、OsSPX-MFS2和OsSPX-MFS3均定位于水稻（稻）原生质体的液泡膜上，即使在没有SPX结构域的情况下也是如此。在高外部Pi浓度下，OsSPX-MFS3在pH 5.5时可部分互补缺乏酵母中所有五种Pi转运蛋白的酵母突变菌株EY917。在卵母细胞中，OsSPX-MFS3被证明根据外部pH和Pi浓度促进Pi流入或流出。与植物细胞中的液泡膜定位相反，当在酵母和卵母细胞中表达时，OsSPX-MFS3定位于质膜。OsSPX-MFS3的过表达导致水稻组织液泡中Pi浓度降低。我们得出结论，OsSPX-MFS3是一种低亲和力Pi转运蛋白，介导Pi从液泡向胞质溶胶的流出并与质子运动偶联。
