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Novel Genomic Locus with Atypical G+C Content that Is Required for Extracellular Polysaccharide Production and Virulence in Xanthomonas oryzae pv. oryzae

November 2001 , Volume 14 , Number  11
Pages  1,335 - 1,339

Sridhar Dharmapuri , J. Yashitola , M. R. Vishnupriya , and Ramesh V. Sonti

Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad-500 007, A. P., India

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Accepted 25 July 2001.

Three exopolysaccharide (EPS)- and virulence-deficient mutants of Xanthomonas oryzae pv. oryzae, the causal agent of bacterial leaf blight of rice, were isolated by Tn5 mutagenesis. These insertions are not located within the gum gene cluster. A 40-kb cosmid clone that restored EPS production and virulence to all three mutants was isolated, and the three transposon insertions were localized to contiguous 4.3- and 3.5-kb EcoRI fragments that are included in this clone. Sequence data indicate that two of the transposon insertions are in genes that encode a putative sugar nucleotide epimerase and a putative glycosyl transferase, respectively; the third insertion is located between the glycosyl transferase gene and a novel open reading frame (ORF). A 5.5-kb genomic region in which these three ORFs are located has a G+C content of 5-1.7%, quite different from the G+C content of approximately 65.0% that is typical of X. oryzae pv. oryzae. Homologues of this locus have not yet been reported in any other xanthomonad.

© 2001 The American Phytopathological Society