Identification of new internal promoters of the Xanthomonas oryzae pathovar oryzae gum gene cluster.

The Xanthomonas oryzae pathovar oryzae gum gene cluster is composed of 14 ORFs designated, in sequence, as gumB to M, XOO3167, and gumN. The gum gene cluster constitutes an operon expressed from multiple promoters located upstream of gumB and gumG, respectively. To identify new promoters responsible for the expression of the gum gene cluster, we have conducted a computer-assisted promoter search and identified previously unreported promoter-like sequences upstream of the gumH and gumM genes, respectively. Moreover, the ability of these putative promoters to stimulate the transcription of the downstream genes was demonstrated by RT-PCR analyses using the mutant strains carrying an insertion of the rrnB transcriptional terminator into the gumG, gumH, and gumL gene, respectively.