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CFP, the Putative Cercosporin Transporter of Cercospora kikuchii, Is Required for Wild Type Cercosporin Production, Resistance, and Virulence on Soybean

October 1999 , Volume 12 , Number  10
Pages  901 - 910

Terrence M. Callahan , 2 Mark S. Rose , 1 , 2 Maura J. Meade , 2 Marilyn Ehrenshaft , 2 and Robert G. Upchurch 1 , 2

1Agricultural Research Service, U.S. Department of Agriculture, and 2Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616 U.S.A.

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Accepted 9 June 1999.

Many species of the fungal genus Cercospora, including the soybean pathogen C. kikuchii, produce the phytotoxic polyketide cercosporin. Cercosporin production is induced by light. Previously, we identified several cDNA clones of mRNA transcripts that exhibited light-enhanced accumulation in C. kikuchii. Targeted disruption of the genomic copy of one of these, now designated CFP (cercosporin facilitator protein), results in a drastic reduction in cercosporin production, greatly reduced virulence of the fungus to soybean, and increased sensitivity to exogenous cercosporin. Sequence analysis of CFP reveals an 1,821-bp open reading frame encoding a 65.4-kDa protein similar to several members of the major facilitator superfamily (MFS) of integral membrane transporter proteins known to confer resistance to various antibiotics and toxins in fungi and bacteria. We propose that CFP encodes a cercosporin transporter that contributes resistance to cercosporin by actively exporting cercosporin, thus maintaining low cellular concentrations of the toxin.

Additional keywords: drug/proton antiporter.

The American Phytopathological Society, 1999