The downturned wing and thorax disruption phenotypes of parkin mutant flies are caused by the degeneration of the IFMs (21,30). Therefore, we investigated whether DmGSTO1 prevented muscle degeneration in park 1 mutants. As determined by histological analysis of thoracic IFMs, the integrity of IFMs in dorsal longitudinal muscles, which regulate adult wing posture, was clearly disrupted in park 1 mutants (Fig. 2E). Although DmGSTO1 null mutants showed a normal muscle phenotype, park 1 /DmGSTO1 null double mutants showed dramatically enhanced degeneration of IFMs compared with park 1 single mutants (Fig. 2E). Furthermore, overexpression of DmGSTO1A using a ubiquitous driver, Tub-Gal4, suppressed the degeneration of IFMs in park 1 mutants. Overexpression of DmGSTO1A in park 1 mutants resulted in regular and compact muscle tissues in the dorsal longitudinal IFMs, which were similar to those of wild type flies except for occasional vacuoles (Fig. 2E). These **data** suggest that DmGSTO1 expression partially rescues the morphological defects and muscle degeneration in park 1 mutants.