Isolation of a Xanthomonas oryzae pv. oryzae flagellar operon region and molecular characterization of flhF

An 8.1-kb DNA fragment from Xanthomonas oryzae pv. oryzae that contains six open reading frames (ORF) was cloned. The ORF encodes proteins similar to flagellar proteins FlhB, FlhA, FlhF, and FliA, plus two proteins of unknown function, ORF234 and ORF319, from Bacillus subtilis and other organisms. T hese ORF have a similar genomic organization to those of their homologs in other bacteria. The flhF gene product, FlhF, has a GTP-binding motif conser ved in its homologs, Unlike its homologs, however, X. oryzae pv. oryzae Flh F carries two transmembrane-like domains. Insertional mutations of the flhF gene with the omega cassette or the kanamycin resistance gene significantl y retard but do not abolish the motility of the bacteria. Complementation o f the mutants with the wildtype flhF gene restored the motility. The X. ory zae pv. oryzae FlhF interacts with itself; the disease resistance gene prod uct XA21; and a protein homologous to the Pill, protein of Pseudomonas aeru ginosa XooPilL, in the yeast two-hybrid system. The biological relevance of these interactions remains to be determined.