Heat shock, copper sulfate and oxidative stress activate the retrotransposon MAGGY resident in the plant pathogenic fungus Magnaporthe grisea

MAGGY is a gypsy-like retrotransposon isolated from the plant pathogenic fu ngus Magnaporthe grisea. The ability of various stresses to activate MAGGY was tested in the original and in a heterologous host (Colletotrichum lagen arium), using beta -glucuronidase (GUS) as a reporter. The MAGGY promoter w as activated in M. grisea by either heat shock, copper sulfate, or oxidativ e stress, but not by the antifungal substance p-coumaric acid. Transcriptio nal up-regulation of MAGGY RNA was also observed following heat shock and o xidative stress. The MAGGY promoter remained responsive to the above-mentio ned stresses when transformed into a M. grisea isolate that had no endogeno us MAGGY elements. In C. lagenarium, however, the MAGGY promoter showed onl y basal expression of GUS and no further up-regulation was induced by any o f the stress treatments, suggesting that the stress-responding cis-elements ) in the MAGGY promoter is not functional in a wider range of fungi. The re lationship between the activation of MAGGY by stress and phenotypic diversi fication in M. grisea, including variations in pathogenicity, is discussed.