Collaborative Research: RESEARCH-PGR: Genome-wide quest for non-host resistance mechanisms in plants

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Globally, ~15% of crop losses are caused by various aggressive pathogens especially fungi, highlighting the importance of crop protection against pathogens. In nature, most plants are resistant to most potential pathogens because of a phenomenon, namely nonhost resistance (NHR). A prime example of NHR is rice’s immunity to rust and powdery mildew diseases that cause serious damages to many other cereal crops including wheat and barley. Hence, NHR provides a major safety barrier for all plants. Unfortunately, due to its genetic complexity, the molecular basis of NHR in most cases remains elusive, which severely limits the exploitation of the immunity mechanisms underlying NHR for improving crop resistance against aggressive pathogens. This multi-institutional collaborative research project aims to dissect genetic and molecular mechanisms of NHR against potential fungal pathogens in two model plants using innovative and combinatorial forward and reverse genetics approaches. Identification and functional characterization of plant immunity genes required for NHR will not only reveal the molecular basis of NHR (which is among the top 10 unanswered questions concerning plant-microbe interactions) but also inspire novel strategies to engineer broader and more robust resistance in crop plants against various pathogens. This project will also generate valuable research materials and tools for the scientific community to study plant immunity mechanisms. Finally, this project will integrate research with education and outreach activities. For example, a “CRISPR Technology and Application” summer workshop in each year will be run by the project team to enhance participation of under-represented minority undergraduate students in plant science.Nonhost resistance (NHR) refers to immunity of most tested genotypes of a plant species to most tested variants of a pathogen species that can cause diseases on other plant species. Unlike host resistance, which is mounted against adapted pathogens and has been well characterized at the molecular level, the genetic basis of NHR remains largely unknown. The long-term goal of this project is to elucidate the molecular mechanisms of NHR for improving crop resistance against aggressive pathogens. It is hypothesized that NHR in most cases is multi-layered and genetically intractable by conventional means but dissectible by stepwise forward genetics and/or CRISPR-enabled reverse genetics approaches. There are four specific objectives for this collaborative project. Aim 1 is to identify novel genes contributing to NHR in Arabidopsis (as a model dicot) against non-adapted powdery mildew and rust fungi using stepwise forward genetic screens. Aim 2 is to identify genes essential for NHR against powdery mildew and rust fungi, and other pathogens in rice (as a model monocot) using multiplexed CRISPR mutagenesis of up to 50 various rice immunity genes followed by geared infection screens. Aim 3 is to elucidate novel immune mechanisms controlling NHR via various molecular methods including comparative transcriptomics, proteomics and metabolomics. Aim 4 is to facilitate community research and promote education of next-generation plant scientists with a focus on training underrepresented minority students. New knowledge from the proposed research may help establish mechanistic frameworks for NHR in connection with the well-established PAMP (pathogen-associated molecular pattern)-triggered immunity and/or effector-triggered immunity.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.