Abstract: Effect of rhizosphere pH on the expression of plasma membrane H+ATPase genes (PMA) in rice (Oryza sativa ssp. japonica cv. Nipponbare) was investigated. Rice seedlings were grown in a solution culture at pH 5.5 as control, and then transferred to the solution at pH 3.5 and 7.5, respectively. Expressions of OsPMA1, OsPMA2, OsPMA3, OsPMA7 were detected in leaves and roots. The expression levels of the PMA genes were lower at pH 3.5 or pH 7.5 than that at pH 5.5. The biomass and N content in rice seedlings decreased with the decreasing pH. The results indicated that the expression of plasma membrane H+ATPase genes in rice roots were inhibited at pH 3.5 by suddenly increased H+ concentration outside plant cells. In this way, the uptake of nutrients driven by plasma membrane H+ATPase was disturbed. Because pH 7.5 in root medium is equivalent to the cytosolic pH value, plasma membrane H+ATPase is not necessary to be overexpressed to overcome the higher H+ gradient across the plasma membrane as at low pH medium (pH 5.5 or pH 3.5). The rest of H+ATPase might be enough for the coupling of nutrient uptake. It is suggested that the rhizosphere pH had great influence on the transcriptional expression of plasma membrane H+ATPase and interfered the nutrient uptake and plant growth.

Key words: rice, plasma membrane, H+ATPase, hydrogen ion concentration(pH), gene expression, rhizophere

摘要： 通过水培试验研究了不同根际pH对水稻(日本晴)细胞膜质子泵基因表达的影响。以栽培在pH 5.5的营养液中的水稻作为对照，然后分别转移到pH 3.5和pH 7.5的营养液中培养。研究发现，质子泵基因OsPMA1、 OsPMA2、OsPMA3、OsPMA7在根系和叶片中均有表达；当营养液pH为3.5或7.5时，上述质子泵基因的表达总体上均比对照（pH 55）降低。但植物地上部的质子泵表达不受根际pH的影响。而且，pH越低，水稻生物量与体内的氮含量越低。其可能的原因是，水稻在pH骤然降为3.5的营养液中没有及时适应高浓度的H+胁迫，导致根系细胞膜质子泵受抑制，进而影响水稻对养分的吸收。而pH 7.5与植物细胞质pH相当，质子泵无需过量表达即可用于养分吸收。说明根际pH直接影响到根系细胞膜质子泵在转录水平上的表达，并间接影响根系对养分的吸收和植物的生长。

关键词: 水稻, 细胞膜, 质子泵, 氢离子浓度指数（pH), 基因表达, 根际