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

植物固定在适当的位置，但可以移动和生长，以响应物理环境。其中一个引人注目的反应是重力：无论植物的位置如何，无论是倒着还是倒着，植物的幼根都会朝着重力的方向生长，朝向地球，而嫩芽将远离重力，向着光线的方向生长。自达尔文时代以来，这种植物对重力刺激的感知和反应一直是一个让科学家们感兴趣的问题。现在已经知道，细胞生长的变化会驱动根的移动，但生长模式是微妙和复杂的。最近发现，在重力响应过程中，根通过弯曲和自我伸直的方式向下生长，这是一种机械上令人费解的但必不可少的现象，与根如何从土壤中获得水分和养分有关。这个项目研究如何使用跨学科的方法进行自我矫正，包括新的成像技术、数学、分子遗传学和基因组学。长期目标是确定控制弯曲的根对重力的反应的基因。了解根是如何进入和穿过土壤生长的，将为操纵和选择更有效的根生长打开大门。随着世界面临不断变化的水资源可获得性和水资源短缺，这项研究可能会揭示可用于作物改良的根系反应。该项目还通过建立博物馆展示，将植物运动的奇迹带给普通公众，其中包括关于根生长的图像和信息。研究生和本科生将接受跨学科生物学研究的培训，以帮助将这些研究推向未来。植物器官具有感知弯曲并通过伸直做出反应的能力，这是一个唤起本体感觉的过程。这种自动伸直反应有助于器官的姿势，这是决定整个工厂结构、生产率和市场价值的重要因素。当受到重力刺激时，短柄蕨根最初的反应是形成强烈的向下弯曲，当根尖与垂直方向成45度角后，曲率下降。在这一点上，根部在经历新一轮弯曲之前伸直。在尖端达到垂直姿势之前，这个过程重复几次。从那时起，根尖继续围绕垂直方向振荡。建立了一个数学模型来概括这些复杂的行为，并用来估计总共46个不同的青兰种质的运动的解释参数。这使得全基因组关联研究的开展成为可能，该研究的目的是确定致病基因。几个DNA多态被发现与振荡的幅度有关。该项目的主要目标是研究这些振荡的细胞特征，并研究控制它们的分子机制。具体目标是：1)表征重力响应过程中曲率和伴随的自动伸直阶段的时空分布；2)研究生长素梯度在它们的调节中的参与；3)利用转录组学和GWAS方法对这些振荡进行分子表征，以确定候选调控因子。这些实验将导致更好地理解管理植物中自动伸直和本体感觉的分子和细胞机制。该奖项反映了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。

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.