BRASSINOSTEROID SIGNALING IN ARABIDOPSIS

植物对光的反应能力对它们的生存至关重要。最近有证据表明油菜素内酯（BRs）与光反应有关，这使得油菜素内酯反应成分的鉴定引起了极大的兴趣。即使在黑暗中生长，不能合成BRs的幼苗也能发育成光照下生长的植物。此外，这些突变体揭示了BRs在整个发育过程中的重要作用。传统的筛选方法试图识别BR反应和信号通路的组成部分，但由于无法发现除BRI1基因外的所有突变，因此受到阻碍。对于为什么在这些筛选中只发现了一个基因，有几种可能的解释。最可能的两种是，BR反应所需的基因参与其他途径（因此产生与BR合成突变体不同的表型）和/或这些基因是多余的或对生存能力至关重要。我将使用新的方法来规避这些障碍，并确定BR信号的新组成部分。在第一种方法中，对不同的拟南芥生态型进行定量性状位点分析将使我能够首先定位然后克隆新的BR响应元件。其次，拟南芥中BR的表征：生长素协同作用将为BR的研究开辟一个新的生态位。这个关于激素通路之间交流的引人注目的例子为更好地理解每种激素的信号以及它们之间的交叉点提供了机会。

Plants' ability to respond to light is crucial for their survival. Recent evidence implicating brassinosteroids (BRs) in the light response has made the identification of brassinosteroid response components of great interest. Seedlings unable to synthesize BRs develop as light-grown plants even when grown in darkness. Moreover, these mutants reveal a significant role for BRs throughout development. Traditional screens attempting to identify components of the BR response and signaling pathway have been hampered by failure to uncover mutations in all but one gene, BRI1. Several explanations for why only one gene was identified in these screens are possible. Two of the most likely are that the genes required for BR response are involved in other pathways (thus yielding phenotypes distinct from BR synthetic mutants) and/or that these genes are redundant or essential for viability. I will use novel approaches to circumvent these obstacles and identify new components of BR signaling. In the first of these approaches, quantitative trait loci analysis on disparate Arabidopsis ecotypes will allow me to first localize and then clone new BR response elements. Secondly, characterization of BR: auxin synergy in Arabidopsis will define a new niche of BR research. This striking example of communication between hormone pathways presents an opportunity to better understand the signaling of each hormone alone as well as the nodes of intersection between them.