Molecular Genetic Investigations of Auto-straightening Using Brachypodium Roots as Model

植物被固定在原地，但可以根据物理环境移动和生长。其中一个显著的反应是对重力的反应：不管植物的位置如何，不管是倒立的还是侧着的，幼苗的根都会朝着重力的方向生长，朝向地球，而芽会朝着远离重力的方向生长，朝着光的方向。植物是如何感知和响应重力刺激的，这是一个自达尔文时代以来150年来一直困扰着科学家的问题。现在已经知道，细胞生长的变化驱动根的运动，但生长模式是微妙和复杂的。最近人们发现，在重力响应过程中，根系以弯曲和自直的方式向下生长，这是一个令人费解的机械现象，但与根系如何从土壤中获取水分和养分有关。该项目利用跨学科的方法，包括新的成像技术、数学、分子遗传学和基因组学，研究了自我矫直是如何发生的。长期目标是确定控制弯曲根对重力反应的基因。了解根系是如何在土壤中生长和穿透土壤的，将为操纵和选择更有效的根系生长打开大门。由于世界面临着不断变化的水分供应和短缺，这项研究可以揭示根系的反应，可以用于作物改良。该项目还通过建立博物馆展示完整的图像和有关根系生长的信息，为公众带来了植物运动的奇迹。研究生和本科生将接受跨学科生物学研究方面的培训，以帮助将这些研究推向未来。植物器官有能力感知弯曲并通过拉直做出反应，这是一个唤起本体感觉的过程。这种自动矫直反应有助于器官的姿势，这是整个植物结构、生产力和市场价值的重要决定因素。当重力刺激时，短柄茅的根最初的反应是形成一个强烈的向下弯曲，当根尖与垂直方向形成45度角后，这种弯曲的速率降低。在这一点上，根在经历新一轮的弯曲之前变直。这个过程反复几次，直到笔尖达到垂直的姿势。从那时起，根尖继续围绕垂直方向摆动。建立了一个数学模型来概括这些复杂的行为，并用于估计总共46个不同的短柄藓属植物的运动解释参数。这使得旨在确定致病基因的全基因组关联研究（GWAS）得以发展。几个DNA多态性被发现与振荡的幅度有关。本项目的主要目的是研究这些振荡的细胞特征，并研究控制它们的分子机制。具体目的是：1)表征重力响应过程中曲率和伴随的自矫直阶段的时空分布；2)研究生长素梯度在其调控中的作用；3)启动这些振荡的分子表征，使用转录组学和GWAS方法确定候选调节因子。这些实验将有助于更好地理解控制植物自拉直和本体感觉的分子和细胞机制。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Plants are anchored in place but can move and grow in response to the physical environment. One such remarkable response is to gravity: regardless of the position of the plant, whether turned upside down or sideways, young plant roots will grow in the direction of gravity, towards the Earth and shoots will grow away from gravity, in the direction of light. How the plant perceives and responds to gravity stimulation is a question that has intrigued scientists a century and a half, since the time of Darwin. It is now known that variations in cell growth drive the movement of roots, but the growth patterns are subtle and complicated. Recently it was discovered that during the gravity response, roots grow down by curving and also self-straightening, a mechanically puzzling but essential phenomenon related to how the roots acquire water and nutrients from the soil. This project investigates how self-straightening occurs using interdisciplinary methods, including novel imaging techniques, mathematics, molecular genetics and genomics. The long-term goal is to identify the genes that control the curving root response to gravity. Understanding how roots grow into and through the soil will open the door to manipulating and selecting for more efficient root growth. As the world faces changing water availability and deficits, this research could uncover root responses that can be harnessed for crop improvements. The project also brings the wonder of plant movement to the general public through establishing museum displays complete with images and information about root growth. Graduate and undergraduate students will be trained in inter-disciplinary biological research to help move these studies into the future.Plant organs have the ability to sense a curvature and respond by straightening, a process that is evocative of proprioception. This auto-straightening response contributes to organ's posture, an important determinant of overall plant architecture, productivity and market value. When gravistimulated, Brachypodium roots initially respond by developing a strong downward curvature whose rate decreases after the tip reaches a 45-degree angle from the vertical. At this point, the root straightens before undergoing a new round of curvature. This process reiterates several times before the tip reaches a vertical posture. From then on, the root tip continues to oscillate around the vertical. A mathematical model was built to recapitulate these complex behaviors, and used to estimate explanatory parameters of the movements for a total of 46 distinct Brachypodium accessions. This allowed the development of a genome-wide association study (GWAS) aimed at identifying contributing genes. Several DNA polymorphisms were found to be associated with the amplitude of the oscillations. The main objective of this project is to investigate the cellular characteristics of these oscillations, and study the molecular mechanisms controlling them. The specific aims are: 1) Characterize the spatio-temporal distribution of curvatures and accompanying auto-straightening phases during a graviresponse; 2) Investigate the involvement of auxin gradients in their regulation, and 3) Initiate a molecular characterization of these oscillations, using transcriptomics and GWAS approaches to identify candidate regulators. These experiments will lead to a better understanding of the molecular and cellular mechanisms that govern auto-straightening and proprioception in plants.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.