Molecular genetic investigation of land plant gravity signaling

当植物在大约4亿年前定居在陆地上时，它们进化出了利用地球的重力矢量作为向导来定向它们的根和芽的生长的能力。潜在的重力传感和响应系统还没有被很好地理解，尽管通过选择性育种对其进行修改已经对当今的农作物和树木产生了重要的影响，预计未来生产力的提高将通过修改来实现，这些修改将导致更陡峭的根更能到达水源，并且在高密度生产场景中，植物拥挤时，幼苗的角度可以更好地拦截光线。该项目旨在确定由基因编码的蛋白质，这些蛋白质构成了拟南芥植物中重力感应机制，这是一般植物的模型。该项目建立在研究的基础上，研究表明，只有在陆地植物中发现的少量懒惰基因编码了重力信号系统的关键组件，该系统定位根和芽。该项目将使用遗传学和生物化学领域的实验方法，寻找与懒惰蛋白一起发挥作用的基因及其蛋白质，以便在细胞内创建一条途径，将重力载体转化为引导生长的生理变化。更清楚地了解这条途径的结构和功能将展示植物如何解决在陆地上生存的挑战，并将创造机会来改进作物植物结构。外展活动将向年轻人介绍如何应对重力。试验计划包括三个部分。第一种是基于突变，这种突变抑制了懒惰的四重突变体的严重向无性生长。一个懒惰四倍体(SLQ)突变体的抑制子已经被确定，另一个正在进行基因定位。SLQ1对懒惰功能有负性调节作用。将研究SLQ1的表达模式、亚细胞定位和作用机制，其他SLQs将在鉴定后进行类似的研究。另一部分是基于在酵母双杂交(Y2H)筛查中发现的LAZY1和一种名为BRXL4的蛋白质之间的功能相关相互作用。Y2H方法将被用来寻找更多的相互作用。蛋白质组筛选将独立地识别LAZY1相互作用子。在整个项目中使用了不同的方法，以增加获得收敛结果的可能性。例如，在SLQ突变筛查中发现的基因可能编码与LAZY1物理上相互作用的蛋白质。遗传、细胞和生化结果将被结合在一起，创建一个重力信号框架。第三部分将测试该框架的机械要素。该项目预计将建立前所未有的关于植物如何使用重力矢量来指导生长的分子细节。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

As plants colonized land some 400 million years ago, they evolved the ability to orient the growth of their roots and shoots using the Earth’s gravity vector as a guide. The underlying gravity sensing and response system is not well understood, even though modification of it through selective breeding has importantly shaped today’s crop plants and trees, and future gains in productivity are expected to attend modifications that result in steeper roots better able to reach water sources, and shoots with angles that intercept light better when plants are crowded in high-density production scenarios. This project aims to identify the proteins, which are encoded by genes, that make up the gravity sensing mechanism in the Arabidopsis thaliana plant, which is a model for plants in general. The project builds off of research indicating that a small number of LAZY genes, found only in land plants, encode key components of the gravity signaling system that orients roots and shoots. The project will use experimental methods from the fields of genetics and biochemistry to find genes and their proteins that function with LAZY proteins to create a pathway within cells that translates the gravity vector into a physiological change that steers growth. A clearer view of this pathway’s structure and function will show how plants solved a challenge to living on land, and it will generate opportunities to improve crop plant architecture. Outreach activities will introduce young members of the public to plant responses to gravity.The experimental plan consists of three sections. The first is based on mutations that suppress the severely agravitropic growth of a lazy quadruple mutant. One of the suppressor of lazy quadruple (slq) mutants has been identified, one more is being genetically mapped. SLQ1 negatively regulates LAZY function. SLQ1 expression pattern, subcellular localization, and mechanism of action will be studied, Other SLQs will be similarly studied after they are identified. Another section is based on a functionally-relevant interaction between LAZY1 and a protein called BRXL4 discovered in a yeast two-hybrid (Y2H) screen. The Y2H method will be used to find additional interactors. A proteomic screen will independently identify LAZY1 interactors. Separate approaches used throughout the project are designed to increase the probability of obtaining convergent results. For example, genes identified in a screen for slq mutations may encode proteins that interact physically with LAZY1. The genetic, cellular, and biochemical results will be combined to create a gravity signaling framework. A third section will test mechanistic elements of the framework. The project is expected to establish an unprecedented level of molecular detail about how plants use the gravity vector to guide growth.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.