Multidrug resistance in Botrytis cinerea associated with decreased accumulation of the azole fungicide oxpoconazole and increased transcription of the ABC transporter gene BcatrD

Azole-resistant mutants of Botrytis cinerea have a multidrug resistance phe notype since they exhibit cross-resistance to unrelated chemicals, These mu tants also display resistance to the new azole fungicide oxpoconazole. Resi stance to oxpoconazole is associated with decreased accumulation of the fun gicide, which is the result of energy-dependent efflux mediated by fungicid e transporters. The ATP-binding cassette (ABC) transporter BcatrB (B. ciner ea ABC transporter B), involved in efflux of phenylpyrrole fungicides, has no major role in efflux of oxpoconazole since accumulation of the fungicide by a replacement mutant of BcatrB showed a transient accumulation pattern similar to that of the wild-type isolate. The putative role of 10 additiona l ABC and 3 Major facilitator superfamily transporters in efflux of oxpocon azole was investigated by expression analysis of the corresponding genes. T he basal transcription level of BcatrD in germlings of B. cinerea was corre lated with the resistance level of two azole-resistant mutants. A short tre atment of germlings with the azole fungicides oxpoconazole, prochloraz, and tebuconazole enhanced transcript levels of BcatrD in a wild-type isolate. Transcript levels induced by these fungicides in azole-resistant mutants al so correlated with resistance levels. We propose that BcatrD is the ABC tra nsporter that plays a role in azole sensitivity and azole resistance of B. cinerea. Expression of BcatrD is also induced by treatment of germlings wit h the dicarboximide fungicide iprodione, the benzimidazole fungicide carben dazim, and the antibiotic cycloheximide. suggesting that this gene indeed p lays a role in multidrug resistance to fungicides. (C) 2001 Academic Press.