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Characterization of Arabidopsis activation-tagged fumonisin B1-resistant (fbr) mutants in programmed cell death (PCD) and plant development
A forward molecular genetics approach was used to isolate gh3.9-1 and D-fbr7 from populations of Arabidopsis activation-tagged T-DNA mutants in a germination/development-based selection scheme to identify fumonisin B1-resistant (fbr) mutants. The characterization of the functions of affected genes in gh3.9-1 and D-fbr7 is the primary focus of the studies presented in this thesis. The GH3.9 gene, belonging to the Arabidopsis Group II primary auxin-responsive GH3 gene family, was found to be affected by the T-DNA insertion in the gh3.9-1 mutant. Phenotypic characterization studies performed with gh3.9-1 mutant along with GH3.9 RNAi lines and additional T-DNA insertions identified in the same region, revealed that GH3.9 might be involved in root development-related processes, as the mutants displayed a long-root length phenotype. GH3.9 expression analysis revealed that GH3.9 transcript accumulation was repressed in seedlings treated with exogenous IAA treatment. Furthermore, gh3.9-1 T-DNA insertions and RNAi lines showed sensitivity to IAA-mediated root growth inhibition and resistance towards Methyl Jasmonate-mediated root growth inhibition. These results have provided new functions for GH3.9 in roots, where it likely controls auxin activity through its amino acid conjugation activity. D-fbr7 was identified as a novel FB1-resistant ( fbr) mutant that was subsequently also found to be defective in embryo development. Different physiological assays conducted to determine resistance of D-fbr7 to FB1-induced cell death at different stages of plant development showed that at both seedling and mature development stages, D-fbr7 displayed resistance to FB1 and FB1-induced senescence. Expression analysis revealed that CLE19, member of CLAVATA3-LIKE (CLE) gene family is involved in causing the fbr phenotype and small RNAs identified in the intergenic region adjacent to D-fbr7 might be involved in conferring embryo lethality. These small RNAs identified by web-based computational approaches were validated by northern expression analysis. These studies have provided evidence of novel roles for CLE19 and small RNAs in affecting plant development.
Khan, Sadaf, "Characterization of Arabidopsis activation-tagged fumonisin B1-resistant (fbr) mutants in programmed cell death (PCD) and plant development" (2007). ETD collection for University of Nebraska - Lincoln. AAI3252836.