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Show 71 college of science Plant innate immunity is a cellular response that defends the organism from infection or disease. Using pattern recognition receptors on the plasma membrane, the cells respond to pathogen-asso-ciated molecular patterns (PAMPs) that typically are derived from specific pathogen-related proteins. The FLS2 protein of the plant Arabidopsis is one of the major PAMP receptors that binds to small protein fragments derived from bacterial flagella. Binding leads to endocytosis of the receptor and activated immune responses. My research involves a mutant called bypass1 (bps1). The normal BPS1 protein functions as a negative regulator of a long-distance signal that is proposed to coordinate shoot growth with conditions perceived by the root. Through an unknown mechanism, the mutant causes leaves to arrest development. My experiments focused on whether the shoot growth arrest phenotype in bps1 mutants is related to innate immunity. Research addressed two questions: (1) Does the reduced growth phenotype of bps1 require the FLS2 receptor?, and (2) Is FLS2 endocytosis the result of the bps1 signal? To determine whether FLS2 was required for shoot growth suppression, I pro-duced bps1 fls2-17 double mutants. We reasoned that if FLS2 was required, then the double mutant would have a more wild type-like phenotype. I found that bps1 fls2 double mutants produced larger leaves than the bps1 single mutant, but the bps1 phenotype was only partially suppressed. This result suggests that activated immune responses are only partially responsible for the bps1 phenotype. To address whether FLS2 was endocytosed in bps1 mutants, I used an FLS2-GFP marker, and compared its localization in the wild type and bps1 mutants. In the wild type, FLS2-GFP is localized on the plasma membrane. We can supply the FLS2 ligand, flg22, which activates endocytosis of the receptor. In bps1 mutants, I found FLS2-GFP in two locations. In cotyledons, it was localized on the plasma membrane. However, in the bps1 leaf primordial, FLS2-GFP was endocytosed. This means innate immunity is evoked in the leaf primordial where the bps1 phenotype is most severe. Future studies will test if the bps1 root is necessary and sufficient for immune responses. This work will assist in understanding cell-to- cell signaling molecules of innate immunity. ARABIDOPSIS GROWTH REGULATION Nisa Fraser (Leslie Sieburth) Department of Biology University of Utah UNDERGRADUATE RESEARCH ABSTRACTS Nisa Fraser Leslie Sieburth |