由α、β和γ三个亚基组成的G-蛋白既专一又精确地将受体感知的胞外信号传递给胞内的下游效应分子。大量的研究结果表明G-蛋白参与植物生长、发育以及逆境胁迫等各种生理生化过程。近年来，在鉴定G-蛋白受体及其调控G-蛋白信号转导的机理研究中取得了突破性进展，但关于G-蛋白效应分子的认识非常有限。我们前期的研究结果发现：诱导表达组成型激活态Gα亚基（Gα*）导致幼苗生长停滞，这为我们解析Gα效应分子提供了很好的切入点。为此，我们构建了突变体库，通过高通量遗传筛选获得了能恢复诱导表达Gα*导致生长停滞表型的突变体（soga）。本项目拟在筛选soga突变体的基础上，分离一批soga基因，通过分子生物学、遗传学和生物化学等手段从中鉴定G-蛋白效应分子，阐明其传递G-蛋白信号的分子机理。相关研究结果将完善我们对G-蛋白信号转导机制的认识，也为将来运用生物技术改良作物品质和抗性奠定理论基础。

Heterotrimeric G-proteins composed of α, β and γ subunits are responsible for transmitting extracellular signals sensed by receptors into cytosolic effectors. In plants, G-proteins have been demonstrated to play important roles in growth, development and responses to various stresses. In the past years, significant advance was made with regard to identification of receptors and mechanisms of G-protein activation. However, how G-proteins tranduce signals to downstream effectors remains largely unknown. Our previous study found that inducible expression of a constitutively active form of the G-protein alpha subunit (Gα*) leads to stagnation of seedling growth, which provides us a promising starting point to investigate effectors of Gα. We therefore established EMS-mutagenized stocks and screened for mutants (suppressors of G-protein alpha, soga) that suppress the stagnation phenotype induced by expression of Gα*. In this proposal, we plan to isolate a batch of soga mutants and to clone genes from soga mutants. Then, we will identify G-protein effectors and elucidate mechanisms by which effectors mediate G-protein signal transduction. Our data will provide new insights into mechanisms of G-protein signaling as well as new ideas to improve crop yields and resistance to stresses.