Comparative proteomic analysis of Xanthomonas citri ssp. citri periplasmic proteins reveals changes in cellular envelope metabolism during in vitro pathogenicity induction

• Published in: Molecular plant pathology 2018-01, Vol.19 (1), p.143-157
• Main Authors: Artier, Juliana, da Silva Zandonadi, Flávia, de Souza Carvalho, Flávia Maria, Pauletti, Bianca Alves, Leme, Adriana Franco Paes, Carnielli, Carolina Moretto, Selistre‐de‐Araujo, Heloisa Sobreiro, Bertolini, Maria Célia, Ferro, Jesus Aparecido, Belasque Júnior, José, de Oliveira, Julio Cezar Franco, Novo‐Mansur, Maria Teresa Marques
• Format: Article
• Language: English
• Subjects: Bacteria; Canker; cell envelope metabolism; citrus canker; differential proteomics; Epimerase; Glucose metabolism; Glucose-1-phosphate; Glucose-1-phosphate thymidylyltransferase; Glyceraldehyde-3-phosphate dehydrogenase; Gram-negative bacteria; Liquid chromatography; Mass spectrometry; Mass spectroscopy; Metabolism; Original; Pathogenicity; Pathogens; Periplasm; periplasmic proteins; Phosphates; Phosphoglucomutase; Plant diseases; Polymerase chain reaction; Post-translation; Proteins; Reactive oxygen species; Spots; Superoxide dismutase; Virulence; Xanthomonas citri; Xanthomonas citri ssp. citri
• ISSN: 1464-6722; 1364-3703
• DOI: 10.1111/mpp.12507

Summary Citrus canker is a plant disease caused by Gram‐negative bacteria from the genus Xanthomonas. The most virulent species is Xanthomonas citri ssp. citri (XAC), which attacks a wide range of citrus hosts. Differential proteomic analysis of the periplasm‐enriched fraction was performed for XAC cells grown in pathogenicity‐inducing (XAM‐M) and pathogenicity‐non‐inducing (nutrient broth) media using two‐dimensional electrophoresis combined with liquid chromatography‐tandem mass spectrometry. Amongst the 40 proteins identified, transglycosylase was detected in a highly abundant spot in XAC cells grown under inducing condition. Additional up‐regulated proteins related to cellular envelope metabolism included glucose‐1‐phosphate thymidylyltransferase, dTDP‐4‐dehydrorhamnose‐3,5‐epimerase and peptidyl‐prolyl cis–trans‐isomerase. Phosphoglucomutase and superoxide dismutase proteins, known to be involved in pathogenicity in other Xanthomonas species or organisms, were also detected. Western blot and quantitative real‐time polymerase chain reaction analyses for transglycosylase and superoxide dismutase confirmed that these proteins were up‐regulated under inducing condition, consistent with the proteomic results. Multiple spots for the 60‐kDa chaperonin and glyceraldehyde‐3‐phosphate dehydrogenase were identified, suggesting the presence of post‐translational modifications. We propose that substantial alterations in cellular envelope metabolism occur during the XAC infectious process, which are related to several aspects, from defence against reactive oxygen species to exopolysaccharide synthesis. Our results provide new candidates for virulence‐related proteins, whose abundance correlates with the induction of pathogenicity and virulence genes, such as hrpD6, hrpG, hrpB7, hpa1 and hrpX. The results present new potential targets against XAC to be investigated in further functional studies.