Environmental and hormonal control of shoot branching

植物的结构高度依赖于枝条的分枝模式。从农艺学的角度来看，分枝的程度很重要，因为它影响生物量和花的数量（因此影响种子），在栽培物种中，它最终影响作物产量。分枝受环境（如温度、水分供应、光周期）和内源性（激素和其他生长调节剂）因素的控制。植物激素生长素被认为是分支的主要调节器，已经被研究了几十年。最近，人们发现了一种新的生长调节剂，叫做独角酯内酯。生长素和独脚金内酯都是负信号，这意味着它们会阻止茎上侧芽的生长，从而减少茎的分枝。第三类生长调节剂，细胞分裂素，作为积极调节剂并促进分支。正是各种激素之间的比例决定了分支是否会发生。环境条件影响分支，可能是因为它们影响了不同激素的水平。我们提出的研究计划旨在确定环境因素影响模式植物拟南芥（Arabidopsis thaliana）中调节茎枝分支的激素依赖信号转导通路的潜在分子机制。我们将使用表现出不同分支水平的野生型和突变植物来确定已知参与生长素反应的三个家族中的哪些蛋白质与茎枝分支特异性相关。我们将鉴定和表征与分支相关的其他候选蛋白，如基因表达的调节因子。因此，拟议的研究计划将使我们能够识别新的分支相关蛋白，并确定环境线索如何与内源性信号相互作用以影响这一非常重要的生理过程。所获得的知识将有助于我们对植物生长决定因素的理解，并将导致开发新的工具来提高植物的性能和产量。

Plant architecture is highly dependent on the pattern of shoot branching. From an agronomical perspective, the degree of branching is important because it affects the biomass and number of flowers (hence seeds), and in cultivated species it ultimately affects crop yield. Branching is controlled by environmental (e.g. temperature, water availability, photoperiod) and endogenous (hormones and other growth regulators) factors. The plant hormone auxin, which has been studied for decades, is considered the master regulator of branching. Recently, novel growth regulators called strigolactones have been identified. Both auxin and strigolactones are negative signals, meaning that they prevent the growth of lateral buds located on the stem, hence reducing shoot branching. A third class of growth regulators, cytokinins, act as positive regulators and promote branching. It is the ratio between the various hormones that determines if branching will occur. Environmental conditions influence branching, likely because they affect the levels of the different hormones. Our proposed research program aims to determine the underlying molecular mechanisms by which environmental factors influence the hormone-dependent signal transduction pathways that regulate shoot branching in the model plant Arabidopsis thaliana. We will use wild-type and mutant plants that show different levels of branching to determine which of the proteins from three families known to be involved in auxin responses are associated specifically with shoot branching. We will identify and characterize other candidate proteins associated with branching, such as regulators of gene expression. The proposed research program will therefore allow us to identify novel branching-associated proteins and determine how the environmental cues interact with endogenous signals to influence this very important physiological process. The knowledge gained will contribute to our understanding of plant growth determinants and will lead to the development of novel tools to improve plant performance and yield.