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TECHNICAL SESSION: Elucidation of plant immune responses to bacterial plant pathogens

What is the role of auxin in root-mediated resistance to Ralstonia solanacearum?
Katherine Rivera-Zuluaga - Purdue University. Anjali Iyer-Pascuzzi- Purdue University, Joshua Widhalm- Purdue University, Manoj Ghaste- Purdue University, Pratibha Choudhary- Purdue University

Bacterial Wilt disease is caused by soilborne plant pathogen Ralstonia solanacearum, which infects economically important crops such as tomatoes, potatoes, peppers, and tobacco. R. solanacearum enters via natural openings in plant roots, invades the xylem tissue, and produces large amounts of exopolysaccharides (EPS) that block water transport, resulting in wilted plants. In tomato, resistance response to R. solanacearum is quantitative and is the result of many genes, however, the molecular basis still remains to be studied. Studies with grafting experiments have shown a significant reduction of Bacterial Wilt. These studies have demonstrated that resistance mechanisms in root are key to plant response. Salicylic acid and jasmonic acid are two plant hormones that play important roles in plant defense responses. Auxin is involved in almost every plant growth process, but recent studies have shown its participation in plant-microbe interactions. However, the role of this hormone in tomato root-mediated resistance to R. solanacearumis unknown. Previous work has shown that a tomato auxin transport mutant diageotropica(dgt 1-1), is resistant to R. solanacearum. RNA-sequencing data from inoculated plants has indicated that auxin-related genes like PIN1, ARFs and IAA/AUXs are downregulated in roots of resistant tomato plant. Preliminary results have identified another auxin transport mutant and an auxin signaling mutant with delayed symptom development. Understanding the role of auxin in defense responses to R. solanacearum in tomato is important for Solanaceae crop improvement.