CYP714B1 and CYP714B2 encode gibberellin 13-oxidases that reduce gibberellin activity in rice
CYP714B1 and CYP714B2 encode gibberellin 13-oxidases that reduce gibberellin activity in rice
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DOI：
10.1073/pnas.1215788110
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发表时间：
2013-01-29
影响因子：
11.1
通讯作者：
Yamaguchi, Shinjiro
中科院分区：
文献类型：
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作者：
Magome, Hiroshi;Nomura, Takahito;Yamaguchi, Shinjiro
生物活性赤霉素 (GA) 控制植物生长和发育的许多方面。 GA(1)是开花植物各种组织中最常见的生物活性GA，但由于催化13-羟基化步骤的酶尚未确定，负责GA(1)生物合成的酶尚未完全阐明。由于缺乏该酶缺陷的突变体，GA 13-羟基化的生物学意义尚不清楚。在这里，我们报道了水稻中的两个细胞色素 P450 基因 CYP714B1 和 CYP714B2 编码 GA 13-氧化酶。过度表达 CYP714B1 或 CYP714B2 的转基因拟南芥植物表现出半矮化。在这些转基因植物中，包括 GA(1) 在内的 13-OH GA 水平有增加的趋势。使用酵母或昆虫细胞进行的功能分析表明，重组CYP714B1和CYP714B2蛋白可以在体外将GA(12)转化为GA(53)(13-OH GA(12))。此外，在水稻cyp714b1 cyp714b2双突变体中，包括GA(1)在内的13-OH GA的水平降低，而包括GA(4)（比GA(1)更活跃）在内的13-H GA的水平升高。这些结果表明CYP714B1和CYP714B2在水稻的GA 13-羟基化中起主导作用。双突变体植物在抽穗前表现出典型的正常表型，但在抽穗期显示出拉长的最上部节间。此外，外源应用生物活性 GA 可以上调 CYP714B1 和 CYP714B2 的表达。我们的结果表明，GA 13-氧化酶通过降低水稻中的 GA 生物活性，在微调植物生长中发挥作用，并且它们还参与 GA 稳态。
Bioactive gibberellins (GAs) control many aspects of growth and development in plants. GA(1) has been the most frequently found bioactive GA in various tissues of flowering plants, but the enzymes responsible for GA(1) biosynthesis have not been fully elucidated due to the enzymes catalyzing the 13-hydroxylation step not being identified. Because of the lack of mutants defective in this enzyme, biological significance of GA 13-hydroxylation has been unknown. Here, we report that two cytochrome P450 genes, CYP714B1 and CYP714B2, encode GA 13-oxidase in rice. Transgenic Arabidopsis plants that overexpress CYP714B1 or CYP714B2 show semidwarfism. There was a trend that the levels of 13-OH GAs including GA(1) were increased in these transgenic plants. Functional analysis using yeast or insect cells shows that recombinant CYP714B1 and CYP714B2 proteins can convert GA(12) into GA(53) (13-OH GA(12)) in vitro. Moreover, the levels of 13-OH GAs including GA(1) were decreased, whereas those of 13-H GAs including GA(4) (which is more active than GA(1)) were increased, in the rice cyp714b1 cyp714b2 double mutant. These results indicate that CYP714B1 and CYP714B2 play a predominant role in GA 13-hydroxylation in rice. The double mutant plants appear pheno-typically normal until heading, but show elongated uppermost internode at the heading stage. Moreover, CYP714B1 and CYP714B2 expression was up-regulated by exogenous application of bioactive GAs. Our results suggest that GA 13-oxidases play a role in fine-tuning plant growth by decreasing GA bioactivity in rice and that they also participate in GA homeostasis.