Proteomics-based identification of differentially abundant proteins reveals adaptation mechanisms of Xanthomonas citri subsp citri during Citrus sinensis infection

Background: Xanthomonas citri subsp. citri (Xac) is the causal agent of citrus canker. A proteomic analysis under in planta infectious and non-infectious conditions was conducted in order to increase our knowledge about the adaptive process of Xac during infection. Results: For that, a 2D-based proteomic analysis of Xac at 1, 3 and 5 days after inoculation, in comparison to Xac growth in NB media was carried out and followed by MALDI-TOF-TOF identification of 124 unique differentially abundant proteins. Among them, 79 correspond to up-regulated proteins in at least one of the three stages of infection. Our results indicate an important role of proteins related to biofilm synthesis, lipopolysaccharides biosynthesis, and iron uptake and metabolism as possible modulators of plant innate immunity, and revealed an intricate network of proteins involved in reactive oxygen species adaptation during Plants'Oxidative Burst response. We also identified proteins previously unknown to be involved in Xac-Citrus interaction, including the hypothetical protein XAC3981. A mutant strain for this gene has proved to be non-pathogenic in respect to classical symptoms of citrus canker induced in compatible plants. Conclusions: This is the first time that a protein repertoire is shown to be active and working in an integrated manner during the infection process in a compatible host, pointing to an elaborate mechanism for adaptation of Xac once inside the plant.Fundacao de Amparo a Pesquisa do Estado de Sao PauloFundacao de Amparo a Pesquisa do Estado de Minas GeraisBIGA grant-CAPESUniv Fed Ouro Preto, Inst Ciencias Exatas & Biol, Dept Ciencias Biol DECBI, Ouro Preto, MG, BrazilUniv Fed Ouro Preto, Nucleo Pesquisas Ciencias Biol NUPEB, Ouro Preto, MG, BrazilUniv Fed Rio de Janeiro, Inst Quim, Dept Bioquim DBq, Rio De Janeiro, RJ, BrazilUniv Estadual Paulista, UNESP, Dept Tecnol, Fac Ciencias Agr & Vet Jaboticabal, Jaboticabal, SP, BrazilUniv Estadual Campinas, UNICAMP, Inst Quim, Campinas, SP, BrazilUniv Sao Paulo, Inst Quim, Dept Bioquim, Sao Paulo, SP, BrazilUniv Fed Sao Paulo UNIFESP, Dept Ciencias Biol, Diadema, SP, BrazilVirginia Tech, Biocomplex Inst, Blacksburg, VA USAUniv Sao Paulo, Inst Quim, Dept Bioquim, Sao Paulo, SP, BrazilUniv Fed Sao Paulo UNIFESP, Dept Ciencias Biol, Diadema, SP, BrazilCAPESFAPESP: 04/02006-7Fundacao de Amparo a Pesquisa do Estado de Minas Gerais: CBB-APQ-04425-10BIGA grant-CAPES: 3385/2013Web of Scienc