根际pH对水稻细胞膜质子泵基因表达的影响

Effect of Rhizosphere pH on the Expression of Plasma Membrane H^+-ATPase Gene in Rice Plants

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(pH5.5)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。

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 overexpressed 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.