Identification of effectors from Xanthomonas citri pv. citri that activate the immune system of the non-host plant Solanum Lycopersicum

• Grant number: 20/04773-8
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: August 01, 2020
• End date: August 01, 2024
• Field of knowledge: Biological Sciences - Biochemistry - Molecular Biology
• Principal Investigator: Paulo José Pereira Lima Teixeira
• Grantee: Caio Vinícius Cardoso Mendes
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

Plants are resistant to the vast majority of pathogens in the environment they inhabit and the occurrence of diseases can be considered an exception to the rule. Resistance against unadapted pathogens is called non-host resistance and is characterized by the fact that all individuals of a given plant species are resistant to all isolates of a pathogen. The molecular mechanisms that determine non-host resistance are still poorly known. Experiments performed in our laboratory revealed that the non-host plant Solanum Lycopersicum (tomato) shows a strong hypersensitivity response (HR) when inoculated with the bacterium Xanthomonas citri pv. citri 306 (Xcc306), which causes citrus canker. Such immune response requires the presence of pathogen effector proteins inside the plant cell since it is non-existent in plants inoculated with the mutant ”(delta)hrpB2, which has the functioning of the type III secretion system compromised. These results suggest that the HR observed in tomato is part of an immune response called Effector Triggered Immunity (ETI), which occurs when one or more effectors of the pathogen are recognized by the plant immune receptors. Thus, this project aims to evaluate whether, in fact, any Xcc306 effector is recognized by tomato. To do so, this plant will be challenged with each of the 30 Xcc306 effectors individually by transient expression mediated by Agrobacterium tumefaciens. Effectors resulting in HR will then be transformed into Xanthomonas gardineri, a naturally pathogenic species in tomato. If a Xcc306 effector is recognized by the tomato immune system, X. gardineri will become avirulent and cause HR in the inoculated leaves, confirming the occurrence of ETI. The results of this project will contribute to the understanding of non-host resistance mechanisms, allowing the future identification of potential immune receptors effective against X. citri. (AU)