title: RecD plays an essential function during growth at low temperature in the antarctic bacterium Pseudomonas syringae Lz4W.
abstract: The Antarctic psychrotrophic bacterium Pseudomonas syringae Lz4W has been used as a model system to identify genes that are required for growth at low temperature. Transposon mutagenesis was carried out to isolate mutant(s) of the bacterium that are defective for growth at 4 degrees but normal at 22 degrees . In one such cold-sensitive mutant (CS1), the transposon-disrupted gene was identified to be a homolog of the recD gene of several bacteria. Trans-complementation and freshly targeted gene disruption studies reconfirmed that the inactivation of the recD gene leads to a cold-sensitive phenotype. We cloned, sequenced, and analyzed approximately 11.2 kbp of DNA from recD and its flanking region from the bacterium. recD was the last gene of a putative recCBD operon. The RecD ORF was 694 amino acids long and 40% identical (52% similar) to the Escherichia coli protein, and it could complement the E. coli recD mutation. The recD gene of E. coli, however, could not complement the cold-sensitive phenotype of the CS1 mutant. Interestingly, the CS1 strain showed greater sensitivity toward the DNA-damaging agents, mitomycin C and UV. The inactivation of recD in P. syringae also led to cell death and accumulation of DNA fragments of approximately 25-30 kbp in size at low temperature (4 degrees ). We propose that during growth at a very low temperature the Antarctic P. syringae is subjected to DNA damage, which requires direct participation of a unique RecD function. Additional results suggest that a truncated recD encoding the N-terminal segment of (1-576) amino acids is sufficient to support growth of P. syringae at low temperature.
authors.affiliation: Centre for Cellular and Molecular Biology, Hyderabad 500007, India.
authors.forename: K
authors.initials: K
authors.lastname: Regha
authors.forename: Ajit K
authors.initials: AK
authors.lastname: Satapathy
authors.forename: Malay K
authors.initials: MK
authors.lastname: Ray
mesh_terms: D000477:Alkylating Agents / Q000494:pharmacology; D000595:Amino Acid Sequence; D000864:Antarctic Regions; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D016923:Cell Death / Q000187:drug effects / Q000528:radiation effects; D003001:Cloning, Molecular; D003080:Cold Temperature; D004247:DNA / Q000032:analysis; D004249:DNA Damage; D004251:DNA Transposable Elements; D004361:Drug Tolerance; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D016685:Mitomycin / Q000494:pharmacology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D016366:Open Reading Frames; D009876:Operon; D044224:Pseudomonas syringae / Q000166:cytology / Q000235:genetics* / Q000254:growth & development*; D011836:Radiation Tolerance; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014466:Ultraviolet Rays
chemical_list: D000477:Alkylating Agents; D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D016685:Mitomycin; D004247:DNA