Crop Biotech Institute & Department of Plant Molecular Systems Biotechnology, Kyung Hee University, Yongin, 446-701, Republic of Korea.
Plant Mol Biol. 2010 Nov;74(4-5):467-78. doi: 10.1007/s11103-010-9687-3. Epub 2010 Sep 28.
Seed germination is an important character for plant growth and seed quality. We identified a rice mutant that was delayed in its germination. There, T-DNA was inserted into Oryza sativa Delayed Seed Germination 1 (OsDSG1), causing a recessive null mutation. Overexpression of the gene enhanced seed germination. OsDSG1 is most similar to Arabidopsis AIP2, an E3 ligase targeting ABI3.Yeast two-hybrid experiments showed that our OsDSG1 binds to OsABI3, indicating that OsDSG1 is a rice ortholog of AIP2. Self-ubiquitination assay indicated that bacterially expressed OsDSG1 protein has E3 ubiquitin ligase activity. Real-time PCR analysis revealed that OsDSG1 was expressed in leaves and roots, and strongly in developing seeds. In addition to the delayed-germination phenotype, mutant plants were shorter and had greater tolerance to high-salt and drought stresses. In the osdsg1 mutant, transcript levels of ABA signaling genes and ABA responsive genes were significantly increased. By contrast, expressions of OsGAMYB and its downstream genes that encode hydrolytic enzymes were markedly reduced. These observations support that OsDSG1 is a major regulator of ABA signaling in germinating seeds. Finally, we observed that the germination rates of various rice cultivars depended upon the transcript levels of OsDSG1 and other ABA-signaling genes.
种子萌发是植物生长和种子质量的重要特征。我们鉴定了一个水稻突变体，其萌发延迟。在那里，T-DNA 插入到水稻延迟种子萌发 1 号（OsDSG1）中，导致隐性纯合突变。该基因的过表达增强了种子萌发。OsDSG1 与拟南芥 AIP2 最为相似，AIP2 是一种靶向 ABI3 的 E3 连接酶。酵母双杂交实验表明，我们的 OsDSG1 与 OsABI3 结合，表明 OsDSG1 是 AIP2 的水稻同源物。自我泛素化测定表明，细菌表达的 OsDSG1 蛋白具有 E3 泛素连接酶活性。实时 PCR 分析显示，OsDSG1 在叶片和根中表达，在发育中的种子中强烈表达。除了萌发延迟表型外，突变体植物更矮，对高盐和干旱胁迫的耐受性更强。在 osdsg1 突变体中，ABA 信号基因和 ABA 响应基因的转录水平显著增加。相比之下，编码水解酶的 OsGAMYB 及其下游基因的表达明显降低。这些观察结果支持 OsDSG1 是萌发种子中 ABA 信号的主要调节剂。最后，我们观察到各种水稻品种的萌发率取决于 OsDSG1 和其他 ABA 信号基因的转录水平。
