This proposal fits the 2009 call for 2010 applications under heading (2) Adaptation to the environment. We “seek to determine the function of Arabidopsis genes and gene networks involved in plant responses to the environment and in adaptation to biotic or abiotic conditions”. Specifically, we are drilling deeply into the control of the intracellular receptors of the plant immune system. Our network begins with RPM1 and the genes required for its function. We continue to identify and analyze new loci required for RPM1 function using ‘second generation’ forward genetics screens. New loci defined by loss of function phenotypes for RPM1 can also be required for other NB-LRR protein functions. We therefore assay NB-LRR protein function to determine the overall rules that regulate their action. RIN4, a key player in disease resistance mediated by RPM1 and another NB-LRR protein called RPS2, is a member of a small family of gene encoding proteins related to RIN4 only via their small (~30aa) plant-specific NOI domains. The ‘NOI’ genes encode proteins of no known function, though the NOI domain contains an AvrRpt2 protease cleavage site (the RCS) and the AvrB binding site (the BBS). We focus on NOI4 and NOI5 which are each required for full RPM1-mediated disease resistance. A combination of genetics (forward and reverse), biochemistry and cell biology is necessary to understand how NB-LRR proteins are assembled into a pre-activation, signal competent state and to define how they are specifically activated after infection. This proposal presents a multi-disciplinary program to approach those goals. 

Crop yield losses to pathogens can be as high as 30%. An increasingly detailed view of how the plant immune system functions to mitigate these losses is emerging from a community focus on the application of Arabidopsis to important problems in plant pathology. The reference plant is useful for studies of nearly all classes of pathogens that are agronomically relevant. Hence, the broader impacts of the proposed research project are that the results will significantly inform translation to crop species. This has already begun with the cloning and utilization of orthologues from crops of relevant genes first identified in Arabidopsis. The use of genetics, molecular biology, biochemistry, and cell biology makes this project an excellent training ground for scientists from undergraduate to post-doctoral levels. Topics investigated in this research project are incorporated into a course taught by the PI on “Strategies of Host-Microbe Interactions”. The PI’s lab has actively sought to engage undergraduates in research projects and the PI is involved in public policy and public debates directly related to the topics of this proposal.