Heterotrimeric GTP-binding protein (G-protein)-mediated abscisic acid (ABA) and drought-stress responses have been documented in numerous plant species. However, our understanding of the function of rice G-protein subunits in ABA signalling and drought tolerance is limited. In this study, the function of G-protein subunits in ABA response and drought resistance in rice plants was explored. It was found that the transcription level of qPE9-1 (rice Gγ subunit) gradually decreased with increasing ABA concentration and the lack of qPE9-1 showed an enhanced drought tolerance in rice plants. In contrast, mRNA levels of RGB1 (rice Gβ subunit) were significantly upregulated by ABA treatment and the lack of RGB1 led to reduced drought tolerance. Furthermore, the results suggested that qPE9-1 negatively regulates the ABA response by suppressing the expression of key transcription factors involved in ABA and stress responses, while RGB1 positively regulates ABA biosynthesis by upregulating NCED gene expression under both normal and drought stress conditions. Taken together, it is proposed that RGB1 is a positive regulator of the ABA response and drought adaption in rice plants, whereas qPE9-1 is modulated by RGB1 and functions as a negative regulator in the ABA-dependent drought-stress responses.
異源三聚體GTP結(jié)合蛋白（G蛋白）介導(dǎo)的脫落酸（ABA）和干旱脅迫響應(yīng)在多種植物中已經(jīng)有了一定研究。但是對(duì)于水稻G蛋白亞基在ABA信號(hào)和干旱耐受性中功能的理解仍比較少。本文研究分析了水稻中G蛋白亞基在ABA響應(yīng)以及抗旱性中的功能。我們發(fā)現(xiàn)qPE9-1（水稻Gγ亞基）的轉(zhuǎn)錄水平隨著ABA含量增加而逐步降低，缺乏qPE9-1的水稻植株表現(xiàn)出耐旱性增強(qiáng)。相比之下，ABA處理會(huì)顯著上調(diào)RGB1（水稻Gβ亞基）mRNA水平，缺少RGB1會(huì)降低耐旱性。此外，這些結(jié)果表明qPE9-1通過抑制參與ABA和脅迫應(yīng)答的關(guān)鍵轉(zhuǎn)錄因子的表達(dá)，負(fù)調(diào)控ABA響應(yīng)，而正常和干旱脅迫條件下RGB1通過上調(diào)NCED基因表達(dá)，正調(diào)控ABA合成。綜上所述，我們認(rèn)為RGB1是水稻ABA響應(yīng)和干旱適應(yīng)性的一個(gè)正調(diào)控因子，而qPE-9受到RGB1介導(dǎo)，作為一個(gè)負(fù)調(diào)控因子在ABA介導(dǎo)的干旱脅迫響應(yīng)中發(fā)揮功能。