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

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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.