Characterization ofkdgR, a gene ofErwinia chrysanthemithat regulates pectin degradation

摘要

SummaryErwinia chrysanthemiis a phytopathogenic enterobacterium able to degrade the pectic fraction of plant cell walls. ThekdgRnegative regulatory gene controls all the genes involved in pectin catabolism, including thepelgenes encoding pectate lyases. TheE. chrysanthemi kdgRregulatory gene was subcloned inEscherichia coliwhere it was shown to be functional, since it repressed the expression of apelE::uidAfusion. The nucleotide sequence ofkdgRcontained an open reading frame of 918bp preceded by classical transcriptional initiation signals. KdgR shows similarity to two other regulatory proteins, namely GylR, encoding an activator protein of the glycerol operon inStreptomyces coelicolor, and IclR, encoding a repressor of the acetate operon inSalmonella typhimuriumand inEscherichia coli.Previously, comparison of regulatory regions of several genes controlled bykdgRrevealed the existence of a conserved region which was proposed as a KdgR‐binding site. The 25 bp oligonucleotide AAAAAAGAAACATTG‐TTTCATTTGT corresponding to this consensus was substituted to thelacoperator, at the beginning of transcription of thelacZgene. This construct functioned as an operator for binding of the KdgR proteinin v