ISOLATION OF 88F ACTIN MUTANTS OF DROSOPHILA-MELANOGASTER AND POSSIBLE ALTERATIONS IN THE MUTANT ACTIN STRUCTURES

The 88F actin (act88F) gene of Drosophila melanogaster encodes an acti n isoform that is expressed exclusively in the indirect flight muscle. In order to isolate a large number of act88F mutants, an efficient sc reening method was used to obtain dominant flightless mutants. Genetic analyses revealed that 25 mutations were located near or at the act88 F locus. From each mutant strain, the DNA fragments including the codi ng region of the act88F gene were asymmetrically amplified by the poly merase chain reaction method, and the amplified fragments were directl y sequenced. Eighteen of them were found to have point mutations withi n their coding regions. Of these, 13 were novel alleles of this gene, We have characterised these mutations in detail. First, their flight a bilities were tested after introducing two normal alleles of this gene . Second, two-dimensional gel electrophoresis was used to examine acti n isoforms and whole thorax proteins. Third, morphological anomalies o f indirect flight muscle fibres and myofibrils were examined with an o ptical microscope. On the basis of these phenotypes and the known atom ic structure of actin, possible alterations in the structure of actin brought about by these mutations are discussed. (C) 1996 Academic Pres s Limited