SEMINAR

Macarena Silva-Guzman Purdue University

Catechol is sufficient to induce Ni resistance in Arabidopsis thaliana Ni toxicity results in reactive oxidative stress causing DNA damage, lipid peroxidation, protein oxidation, and cell damage. Catechol (CA) or 1,2-dihydroxybenzene, is a phenolic compound with antioxidant properties that is accumulated in Brassicaceae species that hyper-accumulate Ni. No role for CA has been previously established in either Ni resistance or Ni accumulation. It is known that CA has an insufficient affinity to Ni for CA-chelation of this cation to have a direct effect on Ni availability. CA does not accumulate in the related the Ni-sensitive model plant Arabidopsis thaliana but ectopic expression of the bacterial enzyme NahG allows us to endogenously produce CA in transgenic A. thaliana. I demonstrated that exogenous CA is sufficient to induce Ni resistance in A. thaliana. CA was sufficient to induce Ni resistance in Arabidopsis only in the presence of gamma-glutamyl-cysteine, which is an intermediate in the biosynthesis of glutathione. Significant increases in cysteine levels and biosynthetic enzyme activities were found when Ni and CA were both present, but no changes in total glutathione were detected. Transcriptional profile analyses by high throughput sequencing of cDNA from roots exposed to Ni, CA and Ni+CA showed that CA increased the expression of genes related to sulfur translocation and assimilation, glutathione reduction, glutathione homeostasis, nicotianamine synthesis, and heat shock response. I carried out a Genome-wide association study (GWAS) of CA response in the presence of Ni and Ni response using primary root length measurements under Ni, CA and Ni+CA as traits. This has identified natural variation in A. thaliana for Ni resistance and detected polymorphisms associated with Ni resistance in linkage with the genes affected in expression levels by CA in the presence or absence of Ni. Based on mutant phenotypes of these genes, metabolite measurements, enzyme activities, transcriptional analyses and high resolution analysis of natural variation CA promotes antioxidant mechanisms resulting in Ni resistance through the regulation of thiol biosynthesis and homeostasis. Despite no adaptation of A. thaliana to high Ni soils variation in ROS suppression, Ni chelation and heat shock proteins results in the protection of plants from oxidation and results in observable variation in response to this toxic environmental contaminant. April 9, 3:30 pm HORT 117

Department of Horticulture and Landscape Architecture