Molecular characterization and expression of the recX gene of Xanthomonas campestris pv. citri.
Two genes important in DNA repair, recA and lexA, were recently identified in Xanthomonas campestris pathovar citri (X.c. pv. citri). An open reading frame located immediately downstream of lexA and recA has now been isolated from this pathovar and characterized. This 486-bp open reading frame encodes a protein of 162 amino acids and shares substantial sequence similarity with recX of other bacterial species. The X.c. pv. citri RecX protein was overexpressed in Escherichia coli and purified; SDS-polyacrylamide gel electrophoresis revealed a molecular size of 18 kDa for the purified protein. Whereas Northern blot analysis failed to detect recX mRNA in X.c. pv. citri, recX transcripts were detected in this pathovar by reverse transcription and polymerase chain reaction analysis. The increased abundance of recX transcript in X.c. pv. citri revealed that the recX promoter was activated by exposure of cells to DNA-damaging agents. Southern blot and polymerase chain reaction analyses revealed the presence of a recX-related gene in all nine additional X. campestris pathovars tested. The genetic arrangement of lexA-recA-recX was apparent in X. campestris and each of the three genes transcribed from their own promoters.
Yang
M K
MK
Department of Biology, Fu Jen University, 510 Chun-Chen Road, Taipei 242, Taiwan, PR China. mkyang@mails.fju.edu.tw
Chou
M E
ME
Yang
Y C
YC
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D003001:Cloning, Molecular; D004249:DNA Damage / Q000502:physiology; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D008163:Luminescent Measurements; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D016133:Polymerase Chain Reaction; D012329:RNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D012697:Serine Endopeptidases / Q000235:genetics; D017361:Viral Nonstructural Proteins / Q000235:genetics; D016959:Xanthomonas campestris / Q000235:genetics* / Q000378:metabolism; D000099160:LexA Repressor Protein
D001426:Bacterial Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012697:Serine Endopeptidases; D017361:Viral Nonstructural Proteins; D000099160:LexA Repressor Protein; C430523:RecX protein, Xanthomonas campestris; C094107:RexA protein, Bacteriophage lambda