RUI: PIRL1 & PIRL9, novel plant Ras-group related LRR proteins essential for male gametophyte function

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Leucine-Rich Repeat proteins (LRRs) constitute a large gene/protein superfamily found in diverse species. LRR domains in these proteins bind specifically to other proteins, and many LRR proteins act in cell signaling networks. PIRLs (Plant Intracellular Ras-group-related LRRs) are a novel family of plant LRRs more closely related to a class of LRRs from animals and yeast than to previously described types of plant proteins. Some related LRR proteins from animals are involved in cell signaling pathways important in cancer and development.This project focuses on PIRL1 and PIRL9, two closely-related PIRL genes from the model plant Arabidopsis thaliana. Preliminary experiments with gene knockout mutants have shown that these genes have redundant and essential roles in pollen development, a process crucial for plant reproduction. The proposed research will employ a combination of genetic, microscopy, and molecular strategies to obtain an integrative understanding the functions of PIRL1 and PIRL9 in plant reproduction, by identifying where these genes act in the context of the whole plant and defining the cellular pathways and biochemical interactions in which they take part. Specific objectives: 1) complete genetic studies of pirl1:pirl9 double mutants and mutant pollen; 2) more precisely define how pirl mutations impact pollen development; 3) determine the sub-cellular locations of PIRL proteins; and 4) investigate biochemical functions by identifying PIRL-binding proteins. An additional objective is to train future U.S. scientists by providing undergraduate research opportunities in post-genomic plant biology: this research will be carried out at an undergraduate college with a high percentage of students who pursue graduate study and careers in biology. By providing insights into plant signal transduction and the genetic requirements for pollen development, this work should ultimately contribute to effective manipulation of plant growth, with benefits for agricultural productivity and plant breeding.