Graduate Student Mississippi State University Starkville, Mississippi
Body of Abstract: In plants, systemic acquired resistance (SAR) provides complete and long-lasting broad-spectrum protection against pathogens through a priming mechanism involving redox and salicylic acid (SA) signaling. However, little is known about the transcriptional dynamics of SAR responses and the redox control of the SAR state. Our previous work identified several key genes in understanding the dynamics of SAR response. Here we observe these dynamics by analyzing the activity of GRXS13 (Glutaredoxins, At1g03850), a disease resistance-related CC-type GRX strongly inducible by SA, using a luciferase reporter system. To achieve this goal, we cloned the promoter region of GRXS13, which carries a luciferase reporter gene, by gateway cloning. We transformed A. thaliana wild-type Columbia ecotype and top2 mutant plants that express GRXS13 gene promoter::Luciferase by using Agrobacterium-mediated floral dip transformation. We tested T1 generation plants for bacterial infiltration by introducing two different types of bacteria (Pseudomonas syringae pv. tomato DC3000 and Pst DC3000 expressing avrRPT2) to prompt SAR. Plants were kept in a darkroom to monitor the bioluminescence signal from the infected leaves. Bioluminescence was monitored and recorded at two hours intervals after infection for four days at 12 h light and 12 h dark diurnal cycle. We observed the oscillatory dynamics of the GRXS13 expression in planta during SAR responses and compared it with the transcriptional response of SAR driver genes we have identified. Comparative analysis of GRXS13 dynamics in Col-0 and the SAR-defective top2 mutant provide insights into how redox signaling dysregulation affects SAR responses. In the future, we plan to analyze the transcriptional dynamics of a larger set of SAR marker genes to understand further the role of redox signaling in plant immunity.