Nakazono M, Tsuji H, Li Y, Saisho D, Arimura S, Tsutsumi N, Hirai A
Laboratory of Plant Molecular Genetics, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
Plant Physiol. 2000 Oct;124(2):587-98. doi: 10.1104/pp.124.2.587.
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 but also can be oxidized by aldehyde dehydrogenase (ALDH). To determine whether ALDH plays a role in anaerobic metabolism in rice (Oryza sativa L. cv Nipponbare), we characterized a cDNA clone encoding mitochondrial ALDH from rice (Aldh2a). Analysis of sub-cellular localization of ALDH2a protein using green fluorescent protein and an in vitro ALDH assay using protein extracts from Escherichia coli cells that overexpressed ALDH2a 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. It is interesting that expression of the rice Aldh2a gene, unlike the expression of the tobacco (Nicotiana tabacum) Aldh2a gene, was induced in rice seedlings by submergence. Experiments with ruthenium red, which is a blocker of Ca(2+) fluxes in rice as well as maize (Zea mays), suggest that the induction of expression of Adh1 and Pdc1 by low oxygen stress is regulated by elevation of the cytosolic Ca(2+) level. However, the induction of Aldh2a gene expression may not be controlled by the cytosolic Ca(2+) level elevation. A possible involvement of ALDH2a in the submergence tolerance of rice is discussed.
已知酒精发酵对于植物在厌氧条件下的存活至关重要。乙醛是酒精发酵的中间产物之一，它不仅能被乙醇脱氢酶还原，还能被乙醛脱氢酶（ALDH）氧化。为了确定ALDH在水稻（Oryza sativa L. cv Nipponbare）厌氧代谢中是否发挥作用，我们对一个编码水稻线粒体ALDH的cDNA克隆（Aldh2a）进行了表征。使用绿色荧光蛋白对ALDH2a蛋白进行亚细胞定位分析，以及使用过表达ALDH2a的大肠杆菌细胞的蛋白提取物进行体外ALDH测定，结果表明ALDH2a在线粒体中乙醛的氧化过程中发挥作用。Southern杂交分析表明，水稻中线粒体ALDH至少由两个基因编码。我们发现Aldh2a mRNA在黑暗生长的幼苗叶片、成熟叶鞘和穗中高水平存在。有趣的是，与烟草（Nicotiana tabacum）Aldh2a基因的表达不同，水稻Aldh2a基因的表达在水稻幼苗中受到淹水诱导。用钌红进行的实验表明，钌红是水稻和玉米（Zea mays）中Ca(2+)通量的阻断剂，低氧胁迫诱导Adh1和Pdc1的表达受胞质Ca(2+)水平升高的调节。然而，Aldh2a基因表达的诱导可能不受胞质Ca(2+)水平升高的控制。本文讨论了ALDH2a可能参与水稻耐淹性的问题。
