Over 30% of the earth's surface is arid, and most climate change models predict future increases in drought length and severity that will adversely affect plant life. Plants adapt to water deprivation in part by fostering root-associated microorganisms that enhance resistance to environmental stresses. The impact of water limitation on molecular communication and the interactions between plants and their associated microbes remains poorly understood. This project will utilize a combination of analytical chemistry, bioinformatics, genetic, and physiological approaches to investigate the mutually beneficial interaction between the root-colonizing bacterium, Pseudomonas synxantha, and wheat under arid conditions. The research will yield new insights into how plants in dry soils recruit, shape, and manipulate their associated microbes to mitigate drought stress. This project will train graduate students and a postdoctoral scholar that will be engaged in all aspects of the research. The analysis of bacterial metabolic pathways will be done by undergraduates via individual research projects and as a part of microbial genetics and ecology classes. The project team will participate in university programs and coordinate outreach activities aimed at recruiting underrepresented groups into the sciences and strengthening science education at the elementary through college levels. This research is crucial for exploitation of beneficial microbial communities to improve crop performance and complement plant breeding efforts.
An overarching goal of this application is to understand at the molecular level how root-colonizing (rhizosphere) bacteria maintain physiological activity and tight mutualistic interactions with their plant hosts in dry soils. Plants can be viewed as meta-organisms or holobionts that rely in part on their microbiome for specific functions and traits. Recent studies have highlighted the essential role of beneficial rhizobacteria in the ability of plants to tolerate abiotic stresses, including drought. However, the effect of water limitation on the plant-microbe communication in the rhizosphere remains virtually unexplored. The approach focuses on Pseudomonas synxantha 2-79, a model biocontrol strain that is naturally adapted to wheat grown in arid parts of the Pacific Northwest. The specific aims are to characterize the changes in wheat root exudates that are associated with water stress and to relate these changes to the physiology of 2-79; to identify transcriptional responses in 2-79 to water-stressed conditions using RNA-seq; and to define the contribution of selected pathways to the ability of 2-79 to persist on roots under conditions of water deficit. The expected results will help to understand how rhizodeposition in arid soils modulates bacterial pathways involved in the mitigation of drought stress and contributes to the selection of specific types of beneficial rhizobacteria. The project will also provide a crucial functional genomics complement to ongoing field studies aimed at deciphering the effect of soil moisture on the rhizosphere microbiome of dryland wheat.
