Abstract
Three DNA regions in Xanthomonas campestris pv. citri which were homologous to the avrBs3 gene family commonly found in Xanthomonas spp. were cloned and their nucleotide sequences were determined. The sequences from 247bp upstream of the translational start to 111bp downstream from the termination site of the open reading frames in these regions were identical except in the tandem repeats of 102bp in the middle of their coding regions. Thus, they contain the same leucine zipper, nuclear localizing signals and inverted repeats as noted by De Feyter et al. Two of them enabled a nonpathogenic mutant missing one of these avrBs3 homologous regions to form a canker, but the remaining one did not even 30 days after inoculation. Comparison of the tandem repeats provided us more information on its organization required for canker formation.
