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Growth Deficiency of a Xanthomonas oryzae pv. oryzae fur Mutant in Rice Leaves Is Rescued by Ascorbic Acid Supplementation

July 2005 , Volume 18 , Number  7
Pages  644 - 651

Sujatha Subramoni and Ramesh V. Sonti

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

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Accepted 11 February 2005.

Xanthomonas oryzae pv. oryzae causes bacterial leaf blight, a serious disease of rice. A mutation was isolated in the ferric uptake regulator (fur) gene of X. oryzae pv. oryzae and it was shown to result in the production of siderophores in a constitutive manner. The fur mutant is hypersensitive to the metallo-antibiotic streptonigrin, a phenotype that is indicative of intracellular free-iron overload, and also exhibits a slow growth phenotype on rich medium. The fur mutant is virulence deficient, hypersensitive to hydrogen peroxide, and exhibits reduced catalase activity. Exogenous supplementation with ascorbic acid (an antioxidant) rescues the growth deficiency of the fur mutant in rice leaves. The virulence deficiency of the X. oryzae pv. oryzae fur mutant is proposed to be due, at least in part, to an impaired ability to cope with the oxidative stress conditions that are encountered during infection.

© 2005 The American Phytopathological Society