Unravelling potential virulence factor candidates inXanthomonas citri. subsp.citriby secretome analysis

Abstract

Citrus canker is a major disease affecting citrus production in Brazil. It’s mainly caused by Xanthomonas citri subsp. citri strain 306 pathotype A (Xac). We analysed the differential expression of proteins secreted by wild type Xac and an asymptomatic mutant for hrpB4 (ΔhrpB4) grown in Nutrient Broth (NB) and a medium mimicking growth conditions in the plant (XAM1). This allowed the identification of 55 secreted proteins, of which 37 were secreted by both strains when cultured in XAM1. In this secreted protein repertoire, the following stand out: Virk, Polyphosphate-selective porin, Cellulase, Endoglucanase, Histone-like protein, Ribosomal proteins, five hypothetical proteins expressed only in the wild type strain, Lytic murein transglycosylase, Lipoprotein, Leucyl-tRNA synthetase, Co-chaperonin, Toluene tolerance, C-type cytochrome biogenesis membrane protein, Aminopeptidase and two hypothetical proteins expressed only in the ΔhrpB4 mutant. Furthermore, Peptidoglycan-associated outer membrane protein, Regulator of pathogenicity factor, Outer membrane proteins, Endopolygalacturonase, Chorismate mutase, Peptidyl-prolyl cis-trans isomerase and seven hypothetical proteins were detected in both strains, suggesting that there was no relationship with the secretion mediated by the type III secretory system, which is not functional in the mutant strain. Also worth mentioning is the Elongation factor Tu (EF-Tu), expressed only the wild type strain, and Type IV pilus assembly protein, Flagellin (FliC) and Flagellar hook-associated protein, identified in the wild-type strain secretome when grown only in NB. Noteworthy, that FliC, EF-Tu are classically characterized as PAMPs (Pathogen-associated molecular patterns), responsible for a PAMP-triggered immunity response. Therefore, our results highlight proteins potentially involved with the virulence. Overall, we conclude that the use of secretome data is a valuable approach that may bring more knowledge of the biology of this important plant pathogen, which ultimately can lead to the establishment of new strategies to combat citrus canker.

Proteome Analysis of Walnut Bacterial Blight Disease

“…The type II secreted proteins are well-characterized in Xanthomonas spp. [ 62 , 63 , 64 ], and many of these proteins are cell wall-degrading enzymes that contribute to bacterial virulence, translocate virulence factors into the plant cells, and facilitate the acquisition of nutrients [ 65 , 66 ]. In addition to type II effectors, Xaj also employs type III effectors, some of which were detected in infected tissues.…”

The ColRS-Regulated Membrane Protein Gene XAC1347 Is Involved in Copper Homeostasis and hrp Gene Expression in Xanthomonas citri subsp. citri

“…By fusion with GFP, we did found that most of XAC1347 protein is bonded to cell membrane ( Supplementary Figure S4A ). As a biotrophic pathogen, Xcc penetrates the apoplast and releases a large number of molecules into the apoplastic space, some of which are pathogen-associated molecular patterns (PAMPs), such as lipopolysaccharides, flagellin or elongation factor Tu ( Facincani et al, 2014 ; Ferreira et al, 2016 ; Carnielli et al, 2017 ). The western blot results indicated that the XAC1347-C-Myc protein was detected from the total cell extract, but not present in the culture supernatant ( Supplementary Figure S4B ).…”

“…An oprB mutant is impaired in biofilm formation, adherence to the host, and virulence ( Ficarra et al, 2017 ). Through proteomics and transposon-based analysis, a large number of outer membrane proteins, transporters and membrane-bound receptors have been identified to be associated with Xcc infection ( Yan and Wang, 2012 ; Facincani et al, 2014 ; Song et al, 2015 ; Ferreira et al, 2016 ; Carnielli et al, 2017 ).…”

Recent Trends in System-Scale Integrative Approaches for Discovering Protective Antigens Against Mycobacterial Pathogens

“…Similar in silico studies have been conducted on various pathogenic genomes and proteomes to identify the repertoire of SASPs which represented novel candidates as virulence factors. These include: Taenia solium ( Gomez et al, 2015 ), Phytophthora infestans ( Raffaele et al, 2010 ), Yersinia pestis ( Yen et al, 2007 ), Xanthomonas citri ( Ferreira et al, 2016 ), Coxiella burnetii ( Ferreira et al, 2016 ), and enteric pathogens including Shigella spp, E. coli , Vibrio cholerae , Yersinia enterocolitica ( Hashmi et al, 2010 ), Salmonella spp. , and Anaplasma marginale ( Palmer et al, 2012 ).…”