Zhu Xiao Fang, Wan Jiang Xue, Sun Ying, Shi Yuan Zhi, Braam Janet, Li Gui Xin, Zheng Shao Jian
State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences (X.F.Z., J.X.W., Y.S, S.J.Z.), and College of Agronomy and Biotechnology (G.X.L.), Zhejiang University, Hangzhou 310058, China;Department of Plant Physiology and Nutrition, Tea Research Institute, Chinese Academy of Agricultural Sciences, the Key Laboratory of Tea Chemical Engineering, Ministry of Agriculture, Hangzhou 310008, China (Y.Z.S.); andBiochemistry and Cell Biology, Rice University, Houston, Texas 77005 (J.B.).
State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences (X.F.Z., J.X.W., Y.S, S.J.Z.), and College of Agronomy and Biotechnology (G.X.L.), Zhejiang University, Hangzhou 310058, China;Department of Plant Physiology and Nutrition, Tea Research Institute, Chinese Academy of Agricultural Sciences, the Key Laboratory of Tea Chemical Engineering, Ministry of Agriculture, Hangzhou 310008, China (Y.Z.S.); andBiochemistry and Cell Biology, Rice University, Houston, Texas 77005 (J.B.)
Plant Physiol. 2014 Aug;165(4):1566-1574. doi: 10.1104/pp.114.243790. Epub 2014 Jun 19.
Previously, we reported that although the Arabidopsis (Arabidopsis thaliana) Xyloglucan Endotransglucosylase-Hydrolase31 (XTH31) has predominately xyloglucan endohydrolase activity in vitro, loss of XTH31 results in remarkably reduced in vivo xyloglucan endotransglucosylase (XET) action and enhanced Al resistance. Here, we report that XTH17, predicted to have XET activity, binds XTH31 in yeast (Saccharomyces cerevisiae) two-hybrid and coimmunoprecipitations assays and that this interaction may be required for XTH17 XET activity in planta. XTH17 and XTH31 may be colocalized in plant cells because tagged XTH17 fusion proteins, like XTH31 fusion proteins, appear to target to the plasma membrane. XTH17 expression, like that of XTH31, was substantially reduced in the presence of aluminum (Al), even at concentrations as low as 10 µm for 24 h or 25 µm for just 30 min. Agrobacterium tumefaciens-mediated transfer DNA insertion mutant of XTH17, xth17, showed low XET action and had moderately shorter roots than the wild type but was more Al resistant than the wild type. Similar to xth31, xth17 had low hemicellulose content and retained less Al in the cell wall. These data suggest a model whereby XTH17 and XTH31 may exist as a dimer at the plasma membrane to confer in vivo XET action, which modulates cell wall Al-binding capacity and thereby affects Al sensitivity in Arabidopsis.
此前，我们报道过，尽管拟南芥木葡聚糖内转糖基酶-水解酶31（XTH31）在体外主要具有木葡聚糖内切水解酶活性，但XTH31的缺失会导致体内木葡聚糖内转糖基酶（XET）活性显著降低，并增强对铝的抗性。在此，我们报道，预测具有XET活性的XTH17在酵母（酿酒酵母）双杂交和免疫共沉淀试验中与XTH31结合，这种相互作用可能是XTH17在植物中发挥XET活性所必需的。XTH17和XTH31可能在植物细胞中共定位，因为与XTH31融合蛋白一样，带有标签的XTH17融合蛋白似乎靶向质膜。与XTH31一样，在铝（Al）存在的情况下，即使在低至10µm浓度处理24小时或25µm浓度仅处理30分钟时，XTH17的表达也会大幅降低。根癌农杆菌介导的XTH17插入突变体xth17表现出低XET活性，根比野生型适度短，但比野生型更耐铝。与xth31相似，xth17半纤维素含量低，细胞壁中保留的铝较少。这些数据表明了一种模型，即XTH17和XTH31可能在质膜上以二聚体形式存在，以赋予体内XET活性，从而调节细胞壁铝结合能力，进而影响拟南芥对铝的敏感性。
