Understanding plant root immunity against the global crop destroyer Macrophomina phaseolina using natural variation in Arabidopsis

由真菌和细菌等病原微生物引起的植物病害造成了巨大的农业损失。被称为“全球作物破坏者”的土传真菌病原菌phaseolina侵染500多种植物的根系，包括许多具有重要经济意义的作物。全球变暖促进了菜绿分枝杆菌的传播。由于对有毒熏蒸方法的限制，这种真菌对美国大田作物生产造成的损失正在增加。因此，迫切需要替代的、创新的方法来减少菜绿芽孢杆菌造成的损害。植物对菜绿分枝杆菌的防御过程了解甚少，根系的免疫是一个研究不足的领域。利用模式植物拟南芥（Arabidopsis thaliana）这一实验研究进展迅速的物种，研究植物根系对phaseolina自然抗病的遗传基础。这项研究有望确定介导植物对这种有害真菌的保护的基因和生物过程。本研究的结果将促进对菜绿支原体抗病性增强的作物品种的开发。其最终目标是减少菜绿分枝杆菌对美国经济的负面影响。这项研究将在加州大学河滨分校进行，这是一所西班牙裔服务机构，也是美国最具种族多样性的研究型大学之一。调查人员坚定地致力于对历史上代表性不足的少数群体成员进行科学培训。以二倍体模式植物拟南芥为研究寄主抗菜绿芽孢杆菌的分子遗传基础，提供了比作物系统更大的优势。拟南芥很容易转化，具有全基因组的突变体和转基因集合，具有非常短的世代时间，并且在最小的空间内生长大量种群。一个特别有用的资源是已确定基因组序列的1000种天然拟南芥的集合。在这个集合中，观察到菜绿分枝杆菌抗性的很大程度的变化，允许防御位点和生物过程有助于对这种有害病原体的根免疫被发现。该项目的中心假设是：拟南芥的自然变异将允许发现根防御菜绿芽孢杆菌的基本机制。研究的具体目标是：(1)利用拟南芥的自然变异揭示对菜绿芽孢杆菌的防御机制。(2)研究根细胞对菜绿芽孢杆菌的特异性免疫反应。(3)确定对菜籽油芽孢杆菌保护的关键位点。通过分析与稻瘟病菌抗性相关的转录模式，将描述宿主对稻瘟病菌免疫的转录控制调控、生理和生化过程。使用根细胞类型特异性荧光标记线，将提供关于不同根组织如何运作以介导对菜绿支原体的保护的信息。反向遗传学和基因定位将鉴定出有助于对菜籽菌产生免疫的植物基因，这可用于为作物的分子遗传育种方法提供信息。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。

Plant diseases caused by pathogenic microbes, such as fungi and bacteria, cause massive agricultural losses. Dubbed a “global destroyer of crops”, the soilborne fungal pathogen Macrophomina phaseolina infects the roots of more than 500 plant species including many economically significant crops. Global warming promotes the spread of M. phaseolina. Losses in US field crop production caused by this fungus are increasing due to restrictions on toxic fumigation methods. Thus, alternative, innovative methods to reduce damage caused by M. phaseolina are urgently needed. Plant defense processes against M. phaseolina are poorly understood and immunity in roots is an understudied area. Taking advantage of the model plant species Arabidopsis thaliana, which allows for rapid progress in experimental studies, the genetic basis of natural disease resistance in plant roots against M. phaseolina will be examined. This study is expected to identify genes and biological processes which mediate protection of plants against this detrimental fungus. Results from this study will accelerate the development of crop cultivars with enhanced disease resistance against M. phaseolina. Its ultimate goal is to reduce the negative impact of M. phaseolina on the U.S. economy. This study will be performed at UC Riverside, a Hispanic Serving Institution, and one of the most ethnically diverse research universities in the USA. The investigators are deeply committed to the scientific training of members of historically underrepresented minority groups.The diploid model plant Arabidopsis thaliana offers substantial advantages over crop systems to study the molecular genetic basis of host resistance against M. phaseolina. Arabidopsis is easily transformed, has genome-wide collections of mutants and transgenics, has a very short generation time, and large populations grow in minimal space. A particularly useful resource is a collection of 1000 natural A. thaliana accessions for which genome sequences have been determined. In this collection, a substantial degree of variation in M. phaseolina resistance is observed, allowing defense loci and biological processes contributing to root immunity against this detrimental pathogen to be uncovered. The central hypothesis of this project is: Natural variation in Arabidopsis thaliana will allow the discovery of fundamental mechanisms of root defenses against M. phaseolina. The specific aims being pursued are:(1) Use natural variation within A. thaliana to uncover defense mechanisms against M. phaseolina.(2) Study root cell type-specific immune responses against M. phaseolina.(3) Identify key loci mediating protection against M. phaseolina. By profiling transcriptional patterns associated with M. phaseolina resistance among A. thaliana accessions a description of transcriptionally-controlled regulatory, physiological, and biochemical processes involved in host immunity against M. phaseolina will be delivered. Using root cell type-specific fluorescent marker lines, information on how distinct root tissues operate to mediate protection against M. phaseolina will be provided. Reverse genetics and gene mapping will identify plant genes that contribute to immunity against M. phaseolina, which can be used to inform molecular genetic breeding approaches in crops.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.