Sample Preparation for Secretome Analysis in A*-Type Strains of Xanthomonas citri subsp. citri, the Causal Agent of Asiatic Citrus Canker Disease

Xanthomonas citri subsp citri (Xcc) is responsible for one of the most destructive diseases of citrus fruits, Asiatic citrus canker. Based on the bacterial host range, the pathogenic forms, A, A*, and Aw have been identified. A*-type strains are not well characterized and they have been reported to differ from other A-type strains on the basis of biochemical and genetic characteristics. In this study, we attempted to develop a medium to mimic in planta conditions for inducing protein secretion of the A*-type strain-NIGEB-088. We also attempted to achieve efficient extraction of Xcc A*-type extracellular proteins, the key mediators of plant-bacterium interaction. Results obtained by this study demonstrate that the m3 (mMM1) can induce Xcc A*-type strains to secret extracellular proteins in amounts detectable by two dimensional gel electrophoresis (2-DE). We also show that Pyrogallol red-molybdate methanol (PRMM) is more effective for precipitation of Xcc A*-type secreted proteins than other assessed procedures of protein precipitation, i. e. acetone, TCA, and sodium deoxycholate