Symbionts as an Additional Defensive Source for the Host: Functional Analysis of the Transcriptome of Symbionts of Diaphorina citri in Response to the Acquisition of the Phytopathogen Candidatus Liberibacter

• Grant number: 13/20581-8
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: March 01, 2014
• End date: February 29, 2016
• Field of knowledge: Agronomical Sciences - Agronomy - Plant Health
• Principal Investigator: Fernando Luis Cônsoli
• Grantee: Fábio Cleisto Alda Dossi
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

Insects play an important role as vectors of plant pathogens, and although insect-associated symbionts have been involved with pathogen acquisition and transmission by insect vectors, there are no information on the physiological mechanisms taking place in the vector-pathogen-symbionts interactions, particularly regarding to host protection against infection. Diaphorina citri harbors two mutualistic bacteria in its bacteriome, Candidatus Carsonella rudii and Candidatus Profftella armatura. While the former maintain a nutritional-based relationship with its host, supplementing host with essential nutrients lacking in the diet, recent functional genomic analysis conferred to the latter an important role in host defense. D. citri stands out as a vector of Candidatus Liberibacter spp., the causative bacteria of Huanglongbing, a devastating citrus disease, even though this insect is not considered an efficiency vector because of the reduced success in acquiring this pathogen. This fact, coupled with the involvement of host-associated symbiotic with the synthesis of defensive bioactive molecules, led us to hypothesize that the acquisition of Liberibacter by D. citri can be influenced by its associated symbionts. In this case, D. citri-associated symbionts could represent a valuable source of biomolecules to be exploited for the control of this devastating citrus disease. As D. citri symbionts and Liberibacter are not culturable, we propose to evaluate the role of D. citri-symbionts in host defense by looking at the response of the symbionts on the process of acquisition and infection of Liberibacter by D. citri through comparative transcriptomic analysis of the bacteriome (RNA-Seq), followed by further evaluation of candidate transcripts by quantitative PCR. The identification of transcripts related to the response to Liberibacter infection will enable the identification of the involved metabolic pathways, and lead to the identification of valuable molecules to be used in the development of new management strategies against this pathogen, including the manipulation of D. citri vectorial competence.