Yamada Nana, Theerawitaya Cattarin, Cha-um Suriyan, Kirdmanee Chalermpol, Takabe Teruhiro
Plant Physiology and Biochemistry Laboratory, National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), Khlong Nueng, Khlong Luang, Pathum Thani, 12120, Thailand.
Protoplasma. 2014 Sep;251(5):1067-75. doi: 10.1007/s00709-014-0615-2. Epub 2014 Jan 31.
Vacuolar Ca2+-transporters could play an important role for salt tolerance in rice (Oryza sativa L.) root. Here, we compared the expression profiles of putative vacuolar cation/H+ exchanger (CAX) and calmodulin-regulated autoinhibited Ca2+-ATPase (ACA) in rice roots of salt tolerant cv. Pokkali and salt sensitive cv. IR29. In addition to five putative vacuolar CAX genes in the rice genome, a new CAX gene (OsCAX4) has been annotated. In the present study, we isolated the OsCAX4 gene and showed that its encoded protein possesses a unique transmembrane structure and is potentially involved in transporting not only Ca2+ but also Mn2+ and Cu2+. These six OsCAX genes differed in their mRNA expression pattern in roots of tolerant versus sensitive rice cultivars exposed to salt stress. For example, OsCAX4 showed abundant expression in IR29 (sensitive) upon prolonged salt stress. The mRNA expression profile of four putative vacuolar Ca2+-ATPases (OsACA4-7) was also examined. Under control conditions, the mRNA levels of OsACA4, OsACA5, and OsACA7 were relatively high and similar among IR29 and Pokkali. Upon salt stress, only OsACA4 showed first a decrease in its expression in Pokkali (tolerant), followed by a significant increase. Based on these results, a role of vacuolar Ca2+ transporter for salt tolerance in rice root was discussed.
液泡Ca²⁺转运蛋白可能在水稻（Oryza sativa L.）根系耐盐性中发挥重要作用。在此，我们比较了耐盐品种Pokkali和盐敏感品种IR29的水稻根系中假定的液泡阳离子/H⁺交换体（CAX）和钙调蛋白调节的自抑制Ca²⁺-ATP酶（ACA）的表达谱。除了水稻基因组中的五个假定液泡CAX基因外，还注释了一个新的CAX基因（OsCAX4）。在本研究中，我们分离了OsCAX4基因，并表明其编码的蛋白质具有独特的跨膜结构，不仅可能参与Ca²⁺的运输，还可能参与Mn²⁺和Cu²⁺的运输。这六个OsCAX基因在耐盐和敏感水稻品种根系中，经盐胁迫处理后的mRNA表达模式存在差异。例如，在长期盐胁迫下，OsCAX4在IR29（敏感品种）中表达丰富。我们还检测了四个假定的液泡Ca²⁺-ATP酶（OsACA4-7）的mRNA表达谱。在对照条件下，IR29和Pokkali中OsACA4、OsACA5和OsACA7的mRNA水平相对较高且相似。盐胁迫后，只有OsACA4在Pokkali（耐盐品种）中的表达先下降，随后显著增加。基于这些结果，讨论了液泡Ca²⁺转运蛋白在水稻根系耐盐性中的作用。
