Exploring mechanisms of TAL-effector recognition and escape from rice and tomato resistance proteins

Bacterial leaf streak (Xanthomonas oryzae pv. oryzicola, Xoc) is a rice pathogen in Africa and Asia. Xo1 is a rice resistance protein which recognizes transcription activator-like effectors (TALEs) from Xoc. Similarly, Bs4 recognizes TALEs from X. campestris pv. vesicatoria (Xcv). However, Asian Xoc strains also carry truncated TALEs (truncTALEs) which suppress Xo1-mediated resistance. My research examines amino acid polymorphisms between the TALE and truncTALE central repeat region (CRR) spine. We ask how these polymorphisms affect activation and suppression of Xo1 and Bs4 resistance by mutating spine residues in TALEs and truncTALEs and quantifying resistance through syringe and clip inoculation assays. We find that TALE spine mutants escape Xo1 resistance, while mutated truncTALEs fail to suppress Xo1, suggesting that Xo1 interacts with the CRR spine of both TALEs and truncTALEs. TALE spine mutants did not escape Bs4 resistance, while truncTALEs did not appear to suppress Bs4, suggesting that Xo1 and Bs4 have different mechanisms of TALE recognition. By understanding how R genes recognizing diverse TALEs work, we will be able to develop broader and more robust resistance to Xoc and potentially other Xanthomonas species.

I am grateful for the opportunity to work with the Bogdanove Lab, especially with the excellent mentorship of my graduate mentor Yumino. By working full-time I’ve experienced a spectrum of the research experience and improved my confidence and independence in the lab. Overall, I appreciate the diversity of research that I’ve been able to see from everyone in the program, and I’m excited to continue unraveling the mysteries of my proteins of interest!