Functional Analysis Of C₄-dicarboxylate Transporter (dctA) Of Xanthomonas Campestris Pv. Campestris

Carbon nutrient is one of the fundamental factors for the successful colonization and expansion of phytopathogenic bacteria in the host aplasma. Generally, glucose is deficient in plant aplasma and bacteria can produce glucose from non-sugar compounds through gluconeogenesis for their growth. Previous studies demonstrated that the gluconeogenesis is involved in the pathogenesis of Xanthomonas campestris pv. campestris (Xcc). C₄-dicarboxylates are main substrates for gluconeogenesis. Therefore, C₄-dicarboxylate transport system may also play an important role in gluconeogenesis of phytopathogenic bacteria. C4-dicarboxylates, like succinate, fumarate, malate and aspartate are transported by C4-dicarboxylate transporter system (Dct). These genes, dctA, dctP and dctQ, were annotated in the genome of Xcc 8004. In this study, the function of dctA is determined by mutation. The mutants is unable to grow on non-carbohydrate minimal medium (NCM) supplemented with fumarate as the sole carbon source and grow poorly on the NCM medium with malate and succinate as the sole carbon source, while wild type strain grow normally on these conditions. This suggested that dctA gene function as a C4-dicarboxylate transporter in Xcc. The virulence of dctA mutant was tested by inoculation on host plant, and results showed that mutation in dctA did not affect virulence of Xcc.