Molecular study on the carAB operon reveals that carB gene is required for swimming and biofilm formation in Xanthomonas citri subsp. citri.
BACKGROUND
The carA and carB genes code the small and large subunits of carbamoyl-phosphate synthase (CPS) that responsible for arginine and pyrimidine production. The purpose of this work was to study the gene organization and expression pattern of carAB operon, and the biological functions of carA and carB genes in Xanthomonas citri subsp. citri.


METHODS
RT-PCR method was employed to identify the full length of carAB operon transcript in X. citri subsp. citri. The promoter of carAB operon was predicted and analyzed its activity by fusing a GUS reporter gene. The swimming motility was tested on 0.25% agar NY plates with 1% glucose. Biofilm was measured by cell adhesion to polyvinyl chloride 96-well plate.


RESULTS
The results indicated that carAB operon was composed of five gene members carA-orf-carB-greA-rpfE. A single promoter was predicted from the nucleotide sequence upstream of carAB operon, and its sensitivity to glutamic acid, uracil and arginine was confirmed by fusing a GUS reporter gene. Deletion mutagenesis of carB gene resulted in reduced abilities in swimming on soft solid media and in forming biofilm on polystyrene microtiter plates.


CONCLUSIONS
From these results, we concluded that carAB operon was involved in multiple biological processes in X. citri subsp. citri.
College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. 000q814035@fafu.edu.cn.
Tao
T
Zhuo
College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. 1540534615@qq.com.
Wei
W
Rou
Hebei Institute of Engineering Technology, Shijiazhuang, 050091, China. songxue86@gamil.com.
Xue
X
Song
School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, 200240, China. gjyeah2012@sjtu.edu.cn.
Jing
J
Guo
College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. 752407929@qq.com.
Xiaojing
X
Fan
College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. gicharukamau@yahoo.com.
Gicharu Gibson
GG
Kamau
College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. hszou@fafu.edu.cn.
Huasong
H
Zou
D018441:Biofilms / Q000254:growth & development*; D002222:Carbamoyl-Phosphate Synthase (Ammonia) / Q000235:genetics* / Q000378:metabolism*; D004252:DNA Mutational Analysis; D020869:Gene Expression Profiling; D023061:Gene Order; D005798:Genes, Bacterial; D017930:Genes, Reporter; D005966:Glucuronidase / Q000032:analysis / Q000235:genetics; D008124:Locomotion; D009876:Operon; D011401:Promoter Regions, Genetic; D017384:Sequence Deletion; D014158:Transcription, Genetic; D014974:Xanthomonas / Q000235:genetics* / Q000502:physiology*
D005966:Glucuronidase; D002222:Carbamoyl-Phosphate Synthase (Ammonia)