The flightless Drosophila mutant raised has two distinct genetic lesions affecting accumulation of myofibrillar proteins in flight muscles.

We have used a combination of histological, molecular, and genetic techniques to investigate the flightless Drosophila mutant raised. Electron microscopy of indirect flight muscles of raised homozygotes confirms that they are grossly abnormal, lacking thin filaments and Z discs. These defects correspond to aberrant protein accumulation in thoraces, where several myofibrillar components are reduced or absent. Utilizing the germ-line transformation technique we demonstrate that one genetic lesion associated with the raised phenotype resides within the act88F actin gene, which, as a result, fails to specify normal mRNA accumulation during thoracic muscle differentiation. We also provide evidence for a distinct second genetic lesion, which apparently eliminates proper posttranslational modification of two myofibrillar proteins, one of which is actin.