Shin Jun-Hye, Kim Sung-Ryul, An Gynheung
National Research Laboratory, Department of Integrative Bioscience and Biotechnology, and Center for Functional Genomics, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea.
Plant Physiol. 2009 Feb;149(2):905-15. doi: 10.1104/pp.108.130716. Epub 2008 Dec 3.
Aldehyde dehydrogenases (ALDHs) catalyze the irreversible oxidation of a wide range of reactive aldehydes to their corresponding carboxylic acids. Although the proteins have been studied from various organisms and at different growth stages, their roles in seed development have not been well elucidated. We obtained T-DNA insertional mutants in OsALDH7, which is remarkably inducible by oxidative and abiotic stresses. Interestingly, endosperms from the osaldh7 null mutants accumulated brown pigments during desiccation and storage. Extracts from the mutant seeds showed a maximum absorbance peak at 360 nm, the wavelength that melanoidin absorbs. Under UV light, those extracts also exhibited much stronger fluorescence than the wild type, suggesting that the pigments are melanoidin. These pigments started to accumulate in the late seed developmental stage, the time when OsALDH7 expression began to increase significantly. Purified OsALDH7 protein showed enzyme activities to malondialdehyde, acetaldehyde, and glyceraldehyde. These results suggest that OsALDH7 is involved in removing various aldehydes formed by oxidative stress during seed desiccation. The mutant seeds were more sensitive to our accelerated aging treatment and accumulated more malondialdehyde than the wild type. These data imply that OsALDH7 plays an important role in maintaining seed viability by detoxifying the aldehydes generated by lipid peroxidation.
醛脱氢酶（ALDHs）催化多种活性醛不可逆地氧化为相应的羧酸。尽管已经对来自各种生物体以及不同生长阶段的这些蛋白质进行了研究，但其在种子发育中的作用尚未得到充分阐明。我们获得了水稻醛脱氢酶7（OsALDH7）的T-DNA插入突变体，该基因在氧化和非生物胁迫下具有显著的诱导性。有趣的是，osaldh7基因敲除突变体的胚乳在干燥和储存过程中积累了棕色色素。突变种子的提取物在360nm处出现最大吸收峰，这是类黑素吸收的波长。在紫外光下，这些提取物也比野生型表现出更强的荧光，表明这些色素是类黑素。这些色素在种子发育后期开始积累，此时OsALDH7的表达开始显著增加。纯化的OsALDH7蛋白对丙二醛、乙醛和甘油醛具有酶活性。这些结果表明，OsALDH7参与清除种子干燥过程中由氧化应激形成的各种醛。与野生型相比，突变种子对加速老化处理更敏感，并且积累了更多的丙二醛。这些数据表明，OsALDH7通过清除脂质过氧化产生的醛，在维持种子活力方面发挥重要作用。
