A novel alkaline α-galactosidase gene is involved in rice leaf senescence
A novel alkaline α-galactosidase gene is involved in rice leaf senescence
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DOI：
10.1007/s11103-004-0641-0
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发表时间：
2004-05-01
影响因子：
5.1
通讯作者：
Chen, SCG
中科院分区：
文献类型：
--
作者：
Lee, RH;Lin, MC;Chen, SCG
我们之前在水稻叶片中分离并鉴定了许多衰老相关基因（SAG）。在这里，我们的结构和功能的SAG-Osh 69编码碱性α-半乳糖苷酶，属于一个新的家庭的糖基水解酶。Osh 69是一个由13个外显子组成的单拷贝基因，位于水稻第8染色体上。Osh 69的表达水平不仅在自然叶片衰老过程中上调，而且在黑暗、激素（甲基茉莉酸、水杨酸）和胁迫（H2 O2和创伤）下也迅速诱导。在大肠杆菌中过表达的重组Osh 69蛋白在pH 8.0时显示出最佳的α-半乳糖苷酶活性。该酶对α-1，6-半乳糖基寡糖和半乳糖脂双半乳糖基甘油二酯具有较好的水解活性。免疫电镜分析表明，Osh 69是专门定位在衰老叶片的叶绿体。这些研究结果强烈表明，在叶片衰老过程中的叶绿体半乳糖脂的降解Osh 69的重要作用。
We previously isolated and identified numerous senescence-associated genes (SAGs) in rice leaves. Here we characterized the structure and function of an SAG-Osh69 encoding alkaline alpha-galactosidase that belongs to a novel family of glycosyl hydrolases. Osh69 is a single-copy gene composed of 13 exons located on rice chromosome 8. The expression level of Osh69 is not only up-regulated during natural leaf senescence but also induced rapidly by darkness, hormones (methyl jasmonic acid, salicylic acid), and stresses (H2O2 and wounding). The recombinant Osh69 protein over-expressed in Escherichia coli has displayed optimal alpha-galactosidase activity at pH 8.0. The enzyme showed good hydrolytic activities towards alpha-1,6-galactosyl oligosaccharides and galactolipid digalactosyl diacylglycerol. Immunoelectron microscopic analysis demonstrates that Osh69 is specifically localized in the chloroplasts of senescing leaves. These findings strongly suggest an important role for Osh69 in the degradation of chloroplast galactolipids during leaf senescence.