Rice dwarf mutant d1, which is defective in the α subunit of the heterotrimeric G protein, affects gibberellin signal transduction

Miyako Ueguchi-Tanaka, Yukiko Fujisawa, Masatomo Kobayashi, Motoyuki Ashikari, Yukimoto Iwasaki, Hidemi Kitano, Makoto Matsuoka

Proceedings of the National Academy of Sciences, 2000, 97(21): 11638-11643  DOI: 10.1073/pnas.97.21.11638;      追溯原文......本站官方QQ群：62473826

Previously, we reported that the rice dwarf mutant, d1, is defective in the α subunit of the heterotrimeric G protein (Gα). In the present study, gibberellin (GA) signaling in d1 and the role of the Gα protein in the GA-signaling pathway were investigated. Compared with the wild type, GA induction of α-amylase activity in aleurone cells of d1 was greatly reduced. Relative to the wild type, the GA₃-treated aleurone layer of d1 had lower expression of Ramy1A, which encodes α-amylase, and OsGAMYB, which encodes a GA-inducible transcriptional factor, and no increase in expression of Ca ^{2 +} -ATPase. However, in the presence of high GA concentrations, α-amylase induction occurred even in d1. The GA sensitivity of second leaf sheath elongation in d1 was similar to that of the wild type in terms of dose responsiveness, but the response of internode elongation to GA was much lower in d1. Furthermore, Os20ox expression was up-regulated, and the GA content was elevated in the stunted internodes of d1. All these results suggest that d1 affects a part of the GA-signaling pathway, namely the induction of α-amylase in the aleurone layer and internode elongation. In addition, a double mutant between d1 and another GA-signaling mutant, slr, revealed that SLR is epistatic to the D1, supporting that the Gα protein is involved in GA signaling. However, the data also provide evidence for the presence of an alternative GA-signaling pathway that does not involve the Gα protein. It is proposed that GA signaling via the Gα protein may be more sensitive than that of the alternative pathway, as indicated by the low GA responsiveness of this Gα-independent pathway.

水稻矮稈突變體d1中異三聚體G蛋白有缺陷，影響了赤霉素信號(hào)傳導(dǎo)

以前，我們報(bào)道了水稻矮稈突變體d1 在異三聚體G蛋白α 亞基(Gα)上有缺陷。本研究研究了d1 中赤霉素(GA)信號(hào)和Gα 蛋白在GA信號(hào)途徑中的作用。與野生型相比，d1 糊粉層細(xì)胞中α-淀粉酶活性的GA 誘導(dǎo)顯著降低。相對(duì)于野生型而言，d1 GA₃處理的糊粉層細(xì)胞中，分別編碼α-淀粉酶和GA誘導(dǎo)的轉(zhuǎn)錄因子的Ramy1A 和OsGAMYB 表達(dá)降低，且Ca²⁺-ATP酶基因表達(dá)沒有增加。然而，當(dāng)高濃度GA下，即使在d1 中也出現(xiàn)α-淀粉酶的誘導(dǎo)。就劑量響應(yīng)而言，野生型與d1 中第2葉鞘延伸的GA 敏感性是類似的，但節(jié)間延伸對(duì)GA 的應(yīng)答比d1 低。而且，d1矮小節(jié)間中，Os20ox 表達(dá)上調(diào)，GA 含量上升。所有這些結(jié)果暗示d1 影響了一部分GA 信號(hào)傳導(dǎo)通路，即糊粉層中α-淀粉酶的誘導(dǎo)和節(jié)間延長(zhǎng)。此外，d1/slr 雙突變揭示SLR 上位于D1，支持了Gα 蛋白參與GA信號(hào)傳導(dǎo)。然而，這些數(shù)據(jù)也證實(shí)了不依賴Gα蛋白的備用GA信號(hào)通路存在。依賴Gα蛋白的GA信號(hào)傳導(dǎo)可能比備用通路更敏感，不依賴Gα通路的低GA響應(yīng)說(shuō)明了這一點(diǎn)。

►基因列表◄
  異三聚體G蛋白α亞基; 矮稈基因 D1; RGA1; D89