Molecular cloning and characterization of an Erwinia carotovora subsp. carotovora pectin lyase gene that responds to DNA-damaging agents

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Abstract
RecA-mediated production of pectin lyase (PNL) and the bacteriocin carotovoricin occurs in Erwinia carotovora subsp. carotovora 71 when this organism is subjected to agents that damage or inhibit the synthesis of DNA. The structural gene pnlA was isolated from a strain 71 cosmid gene library following mobilization of the cosmids into a moderate PNL producer, strain 193. The cosmid complemented pnl::Tn5 but not ctv::Tn5 mutations. A constitutive level of PNL activity was detected in RecA+ and RecA- Escherichia coli strains carrying the pnlA+ gene on the high-copy-number plasmid pBluescript SK-. Mappings of Mu dI1734 (Km lac'ZYA) insertions in pnlA and unidirectional deletion analyses allowed localization of the gene to approximately 1.4 kilobases of DNA. A typical pnlA-lacZ transcriptional fusion was inducible in a RecA+ but not a RecA- derivative of strain 71. In contrast, the pnlA-lacZ fusion was not inducible in a RecA+ E. coli strain. DNA sequences homologous to pnlA were detected in E. carotovora subsp. carotovora and E. carotovora subsp. atroseptica strains and in one of four Erwinia rhapontici strains but not in Erwinia chrysanthemi.