UC San Diego

Plants are exposed to many stresses, including drought and pathogens. The phytohormone abscisic acid (ABA) is known to regulate major abiotic stress responses. The hormones salicyclic acid (SA), jasmonic acid (JA), and ethylene (ET) are known to regulate biotic stresses. Previous research has identified a molecule, [5-(3,4- dichlorophenyl) furan-2-yl]-piperidine-1-ylmethanethione (DFPM) that negatively regulates ABA signaling by activating a plant immune signaling pathway (Kim et al., 2011). In Chapter 1, the mutants reduced sensitivity to DFPM-inhibition of ABA (rda1 and rda2) are characterized by developing a method to genetically map the rda2 and rda1 loci to characterize their roles in mediating cross talk of an effector-triggered biotic stress response with abscisic acid (ABA) signal transduction. Through these mutants, the connection between abiotic and biotic stress signaling could uncover new insights. In addition, plants are also stressed if exposed to toxic metal(loid)s and one strategy plants use is to activate the sulfate assimilation pathway in order to enhance synthesis of thiols for detoxification of metal(loid)s. The mechanisms mediating metal(loid)-induced gene expression remain poorly understood. In Chapter 2, Slim1, a key regulator of the sulfate assimilation pathway during sulfur starvation, is investigated for its role in metal(loid) detoxification. To further identify activators and repressors of the pathway, a screen of an amiRNA library targeting transcription factors is screened on cadmium. Understanding the regulation of this pathway is thus an integral part of engineering plants that either prevent metal accumulation in edible plant tissues or alternatively accumulate high levels of toxic compounds for phytoremediation