UC San Diego

Abstract

Being sessile organisms, plants have evolutionarily developed a variety of mechanisms to protect themselves from biotic and abiotic stressors such as pathogen exposure, drought conditions, and heavy metal contamination. The phytohormone, abscisic acid (ABA), is a major stress hormone in Arabidopsis thaliana essential for resistance to abiotic stressors, such as drought conditions. In addition to mediating drought tolerance, however, ABA has been found to interfere with pathogen resistance signaling as well by increasing susceptibility to pathogens. Recent discoveries demonstrated a novel interference in plant stress signaling-- ABA signal repression by pathogen defense activation by the small molecule [5-(3,4-dichlorophenyl)furan-2-yl]- piperidine-1-yl methanethione (DFPM). In Chapter 1, fluorescence microscopy and genetic analysis techniques are utilized in attempts to identify a mutant found to be resistant to DFPM inhibition of ABA signal transduction. Experimental findings include a growth phenotype of this mutant and approximate candidate genes of the rda1 causative mutation. In Chapter 2, a novel chemical genetics screen utilizing an artificial microRNA library was developed to identify genetic components necessary for a DFPM induced root-specific meristematic cell death signaling pathway. Study findings include the establishment of a robust chemical genetics screen, demonstration of mutant phenotypes, and identification of a DFPM-resistant mutant candidate which repeatedly demonstrated a root growth continuation phenotype.