Function of the α Subunit of Rice Heterotrimeric G Protein in Brassinosteroid Signaling
Function of the α Subunit of Rice Heterotrimeric G Protein in Brassinosteroid Signaling
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DOI：
10.1093/pcp/pcn182
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发表时间：
2009-01-01
影响因子：
4.9
通讯作者：
Iwasaki, Yukimoto
中科院分区：
文献类型：
--
作者：
Oki, Katsuyuki;Inaba, Noriko;Iwasaki, Yukimoto
植物异三聚体G蛋白(G)亚基在植物发育和对激素的反应等多个方面起着关键作用。最近，一些证据表明G参与拟南芥和水稻的油菜素内酯（BR）反应。在这项研究中，我们利用G基因的缺陷突变体T65d1，全面分析了水稻G在BR反应中的作用。T65d1突变体对24-epi-油菜素内酯（24-epiBL）的敏感性降低在许多过程中被观察到，例如在抑制根生长和促进胚芽伸长方面。T65d1突变体也表现出与br缺陷突变体相似的表型，例如在黑暗条件下特异性缩短的第二节间和组成型光形态生长表型。然而，在T65d1突变体中观察到24-epiBL对BR生物合成基因表达的负反馈效应，并且该突变体中BR中间体的水平没有波动。为了确定T65d1突变体与水稻BR受体突变体弱等位基因d61-7之间的上位性关系，对这两个突变体进行了杂交。双突变体T65d1/d61-7在节间伸长抑制、节间伸长模式、叶片角度和叶片形态异常等方面均未表现上位性，但种子垂长和种子重有显著差异。我们的研究结果表明，水稻G影响BR信号级联，但G可能不是bri1介导的感知/转导的信号分子。
The subunit of plant heterotrimeric G proteins (G) plays pivotal roles in multiple aspects of development and responses to plant hormones. Recently, several lines of evidence have shown that G participates in brassinosteroid (BR) responses in Arabidopsis and rice plants. In this study, we conducted a comprehensive analysis of the roles of the rice G in the responses to BR using a defective mutant of the G gene, T65d1. Decreased sensitivity to 24-epi-brassinolide (24-epiBL) in the T65d1 mutant was observed in many processes examined, e.g. in the inhibition of root growth and the promotion of coleoptile elongation. The T65d1 mutant also showed similar phenotypes to those of BR-deficient mutants, such as the specifically shortened second internode and the constitutive photomorphogenic growth phenotype under dark conditions. However, a negative feedback effect by 24-epiBL on the expression of BR biosynthetic genes was observed in the T65d1 mutant, and the levels of BR intermediates did not fluctuate in this mutant. To determine the epistatic relationship between the T65d1 mutant and d61-7, a weak allele of a rice BR receptor mutant, the two mutants were crossed. The T65d1/d61-7 double mutant showed no epistasis in the elongation inhibition of the internodes, the internode elongation pattern, the leaf angle and the morphological abnormality of leaf, except for the vertical length of seed and the seed weight. Our results suggest that the rice G affects the BR signaling cascade but the G may not be a signaling molecule in BRI1-meditated perception/transduction.