中文摘要：

Carbamoyl-phosphate synthase plays a vital role in the carbon and nitrogen metabolism cycles. In Xanthomonas citri subsp. citri, car A and car B encode the small and large subunits of carbamoyl-phosphate synthase, respectively. The deletion mutation of the coding regions revealed that car A did not affect any of the phenotypes, while car B played multiple roles in pathogenicity. The deletion of car B rendered the loss of pathogenicity in host plants and the ability to induce a hypersensitive reaction in the non-hosts. Quantitative reverse transcription-PCR assays indicated that 11 hrp genes coding the type III secretion system were suppressed when interacting with citrus plants. The mutation in car B also affected bacterial utilization of several carbon and nitrogen resources in minimal medium MMX and extracellular enzyme activities. These data demonstrated that only the large subunit of carbamoyl-phosphate synthase was essential for canker development by X. citri subsp. citri.

英文摘要：

Carbamoyl-phosphate synthase plays a vital role in the carbon and nitrogen metabolism cycles. In Xanthomonas citrisubsp. citri, carA and carB encode the small and large subunits of carbamoyl-phosphate synthase, respectively. The deletion mutation of the coding regions revealed that carA did not affect any of the phenotypes, while carB played multiple roles in pathogenicity. The deletion of carB rendered the loss of pathogenicity in host plants and the ability to induce a hyper- sensitive reaction in the non-hosts. Quantitative reverse transcription-PCR assays indicated that 11 hrp genes coding the type Ill secretion system were suppressed when interacting with citrus plants. The mutation in carB also affected bacterial utilization of several carbon and nitrogen resources in minimal medium MMX and extracellular enzyme activities. These data demonstrated that only the large subunit of carbamoyl-phosphate synthase was essential for canker development by X. citri subsp, citri.