The α-amylase induction in endosperm during rice seed germination is caused by gibberellin synthesized in epithelium
The α-amylase induction in endosperm during rice seed germination is caused by gibberellin synthesized in epithelium
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DOI：
10.1104/pp.010785
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发表时间：
2002-04-01
期刊：
影响因子：
7.4
通讯作者：
Matsuoka, M
中科院分区：
文献类型：
--
作者：
Kaneko, M;Itoh, H;Matsuoka, M
我们最近从水稻 (Oryza sativa) 中分离出两个编码 3β-羟化酶的基因 (OsGA3ox1 和 OsGA3ox2)，该酶催化活性赤霉素 (GA) 生物合成的最后一步 (H. Itch, M. Ueguchi-Tanaka, N. Sentoku, H. Kitano, M. Matsuoka, M. Kobayashi [2001] Proc Natl Acad Sci USA 98：8909-8914）。利用这些克隆的 cDNA，我们分析了水稻种子萌发过程中 3β-羟化酶基因和 α-淀粉酶基因 (RAmy1A) 的时空表达模式，以研究 GA 生物合成与 α-淀粉酶表达之间的关系。 Northern印迹分析显示，胚胎中的RAmy1A表达发生在3β-羟化酶表达诱导之前，而在胚乳中，高水平的RAmy1A表达发生在OsGA3ox2表达峰值后1至2天，并且仅在不存在烯效唑的情况下发生。基于对 OsGA3ox2 无效突变体（d18-Akibare 矮人）的分析，我们确定 OsGA3ox2 产生的 3β-羟化酶对于诱导 RAmy1A 表达很重要，而 OsGA3ox1 产物对于 α-淀粉酶诱导不是必需的。 OsGA3ox2 的表达定位于胚胎的芽区域和上皮，强烈表明活跃的 GA 生物合成发生在这两个区域。上皮中活性 GA 的合成对于胚乳中 α-淀粉酶的表达非常重要，因为芽形成缺陷但上皮细胞发育的胚胎突变体诱导胚乳中 α-淀粉酶表达，而上皮发育缺陷的突变体则不然。
We recently isolated two genes (OsGA3ox1 and OsGA3ox2) from rice (Oryza sativa) encoding 3beta-hydroxylase, which catalyzes the final step of active gibberellin (GA) biosynthesis (H. Itch, M. Ueguchi-Tanaka, N. Sentoku, H. Kitano, M. Matsuoka, M. Kobayashi [2001] Proc Natl Acad Sci USA 98: 8909-8914). Using these cloned cDNAs, we analyzed the temporal and spatial expression patterns of the 3beta-hydroxylase genes and also an alpha-amylase gene (RAmy1A) during rice seed germination to investigate the relationship between GA biosynthesis and alpha-amylase expression. Northern-blot analyses revealed that RAmy1A expression in the embryo occurs before the induction of 3beta-hydroxylase expression, whereas in the endosperm, a high level of RAmy1A expression occurs 1 to 2 d after the peak of OsGA3ox2 expression and only in the absence of uniconazol. Based on the analysis of an OsGA3ox2 null mutant (d18-Akibare dwarf), we determined that 3beta-hydroxylase produced by OsGA3ox2 is important for the induction of RAmy1A expression and that the OsGA3ox1 product is not essential for alpha-amylase induction. The expression of OsGA3ox2 was localized to the shoot region and epithelium of the embryo, strongly suggesting that active GA biosynthesis occurs in these two regions. The synthesis of active GA in the epithelium is important for a-amylase expression in the endosperm, because an embryonic mutant defective in shoot formation, but which developed epithelium cells, induced alpha-amylase expression in the endosperm, whereas a mutant defective in epithelium development did not.