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Mutants of Xanthomonas oryzae pv. oryzae Deficient in General Secretory Pathway Are Virulence Deficient and Unable to Secrete Xylanase

April 2000 , Volume 13 , Number  4
Pages  394 - 401

Suvendra K. Ray , R. Rajeshwari , and Ramesh V. Sonti

Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad-500007, India

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Accepted 6 January 2000.

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial leaf blight, a serious disease of rice. A virulence- and xylanase-deficient mutant of Xoo was isolated following ethyl methane sulfonate (EMS) mutagenesis. A cosmid clone that restored virulence and xylanase secretion was obtained from a genomic library by functional complementation. Trans-poson mutagenesis and marker exchange studies revealed genes on the cloned DNA that were required for xylanase production and virulence. Sequence analysis with trans-poson-specific primers revealed that these genes were homologues of xps F and xps D, which encode components of a protein secretion system in Xanthomonas campestris pv. campestris. Enzyme assays showed xylanase accumulation in the periplasmic space and cytoplasm of the xps F mutant and the complementing clone restored transport to the extracellular space.

Additional keywords: type II protein secretion.

© 2000 The American Phytopathological Society