Exploring Non-host plant as sources of immune receptors capable of recognizing citrus pathogens

• Grant number: 25/09764-0
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: November 01, 2025
• End date: February 28, 2029
• Field of knowledge: Biological Sciences - Biochemistry - Molecular Biology
• Principal Investigator: Paulo José Pereira Lima Teixeira
• Grantee: Amanda Nicolau Minetto
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

In nature, all plants are in constant interaction with a huge diversity of pathogenic microorganisms. However, most plants are naturally resistant to most of these pathogens, making the occurrence of diseases an exception. Interestingly, pathogens that are highly destructive to a plant species are often avirulent in unrelated species, characterizing the phenomenon of non-host resistance, in which all individuals of a species are resistant to all variants of a pathogen. Among the multiple factors that can contribute to non-host resistance, immune receptors of the NLR (Nucleotide-binding leucine-rich repeat) family may play a central role in determining the compatibility between various plants and pathogens. Historically, the study of plant molecular immunology has focused mainly on receptors involved in immunity within the host species itself. In contrast, the role of immune receptors in resistance of non-host species remains relatively unexplored. Each individual of a plant species may contain hundreds or even thousands of NLRs, and the composition of these receptors is highly variable, both among individuals and among species. Thus, the plant kingdom represents an immense and unexplored source of genetic diversity, with the potential to reveal highly effective receptors against pathogens of agricultural importance. In view of this, this project aims to investigate non-host plants in search of immune receptors capable of recognizing two pathogens of great relevance to citrus farming: Candidatus liberibacter asiaticus (which causes citrus greening) and Xanthomonas citri subsp. citri (which causes citrus canker). To this end, we will express effectors of these pathogens in non-host plants via transient expression mediated by Agrobacterium, in order to observe whether any of them is capable of triggering an immune response mediated by the recognition of these effectors. The plants used will be previously subjected to tests to verify whether they are resistant to agroinfiltration. These assays will be performed by means of the constitutive expression of the betalain pigment through the RUBY reporter cassette, which confers a reddish coloration to the plant tissue, indicating the compatibility of the plant with the agroinfiltration process. After identifying plants capable of recognizing one or more evaluated effectors, an investigation will be conducted to determine the receptor(s) involved in this recognition. Then, the functional characterization of the identified receptor(s) will be performed, aiming to understand their role in the defense mechanism. Preliminary experiments have already revealed the existence of potential receptors capable of recognizing some of the effectors of X. citri subsp. citri, reinforcing the effectiveness of the proposed strategy. We hope that this approach can reveal promising resources still hidden in the genetic diversity of the plant kingdom, paving the way for the development of innovative and sustainable strategies for the control of agricultural diseases. (AU)