Molecular breeding for submergence tolerance in crops

众所周知，酒精发酵对植物在厌氧条件下的生存很重要。乙醛是酒精发酵的中间体之一，它不仅可以被乙醇脱氢酶（ADH）还原，还可以被醛脱氢酶（ALDH）氧化。为了确定ALDH是否在水稻（Oryza sativa L.）的厌氧代谢中发挥作用，我们鉴定了一个编码水稻线粒体ALDH的cDNA克隆（Aldh2a）。ALDH2a蛋白亚细胞定位分析和体外ALDH测定表明，ALDH2a在线粒体中乙醛氧化中起作用。Southern blot分析表明，水稻线粒体ALDH至少由两个基因编码。我们发现Aldh2a mRNA在深色生长的幼苗叶片、成熟叶鞘和穗中表达水平较高。有趣的是，与烟草Aldh2a基因的表达不同，水稻Aldh2a基因的表达在水稻幼苗中被淹没诱导。研究了ALDH2a基因对水稻耐淹性的影响。

It is known that alcoholic fermentation is important for survival of plants under anaerobic conditions. Acetaldehyde, one of the intermediates of alcoholic fermentation, is not only reduced by alcohol dehydrogenase (ADH) but also can be oxidized by aldehyde dehydrogenase (ALDH). To determine whether ALDH plays a role in anaerobic metabolism in rice (Oryza sativa L.), we characterized a cDNA clone encoding mitochondrial ALDH from rice (Aldh2a). Analysis of subcellular localization of ALDH2a protein and an in vitro ALDH assay indicated that ALDH2a functions in the oxidation of acetaldehyde in mitochondria. A Southern blot analysis indicated that mitochondrial ALDH is encoded by at least two genes in rice. We found that the Aldh2a mRNA was present at high levels in leaves of dark-grown seedlings, mature leaf sheaths and panicles. Interestingly, expression of the rice Aldh2a gene, unlike the expression of the tobacco Aldh2a gene, was induced in rice seedlings by submergence. A possible involvement of ALDH2a in the submergence tolerance of rice was studied.