Genetic Analysis of Alpha-Tubulin Function in Drosophila

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Tubulin plays a crucial role in morphogenesis as the primary component of microtubules. We propose to address two basic questions about these important structural proteins using the four a-tubulins of Drosophila: are any of the a-tubulin isotypes functionally specialized, and what regulatory mechanisms are responsible for achieving the correct ratios and concentrations of a-tubulins isotypes in each cell type? The multifunctionality of each a-tubulin isotype will be tested by determining the ability of one isotype to rescue developmental defects associated with mutations in another isotype. Transgenic strains carrying ectopic copies of each a-tubulin gene and mutations in two of the a- tubulins are available. An attempt will be made to generate mutations in the two remaining genes using P-element mutagenesis and PCR, an approach that allows the recovery of mutations with no detectable phenotype. Regulatory mechanisms operating to maintain tissue-appropriate a-tubulin pools will be identified by examining the ability of cells to 1) eliminate misexpressed a-tubulin isotypes produced from chimeric genes, and 2) respond to overexpression of appropriate isotypes from supernumerary tubulin genes. Genes encoding transacting a-tubulin regulatory factors will be sought by reverting the female sterility associated with overexpression of a maternal tubulin. The protein tubulin is an important structural component of most types of cells. It exists in a number of different forms, some present in all cells, others present only in certain specialized types of cells. The different forms of tubulin presumably serve different functions, but very little is known about what these functions are. This is a proposal to investigate the different functions of the different forms of tubulin.