Interacting genes that affect microtubule function in Drosophila melanogaster: Two classes of mutation revert the failure to complement between hay(nc2) and mutations in tubulin genes

Abstract

The recessive male sterile mutation hay(nc2) of Drosophila melanogaster fails to complement certain β2-tubulin and α-tubulin mutations, suggesting that the haywire product plays a role in microtubule function, perhaps as a structural component of microtubules. The genetic interaction appears to require the presence of the aberrant product encoded by hay(nc2), which may act as a structural poison. Based on this observation, we have isolated ten new mutations that revert the failure to complement between hay(nc2) and B2t(n). The revertants tested behaved as intragenic mutations of hay in recombination tests, and fell into two phenotypic classes, suggesting two functional domains of the hay gene product. Some revertants were hemizygous viable and less severe than hay(nc2) in their recessive phenotype. These mutations might revert the poison by restoring the aberrant product encoded by the hay(nc2) allele to more wild-type function. Most of the revertants were recessive lethal mutations, indicating that the hay gene product is essential for viability. These more extreme mutations could revert the poison by destroying the ability of the aberrant haywire(nc2) product to interact structurally with microtubules. Flies heterozygous for the original hay(nc2) allele and an extreme revertant show defects in both the structure and the function of the male meiotic spindle.