Drosophila β-Tubulin 97EF is upregulated at low temperature and stabilizes microtubules.

Cells in ectotherms function normally within an often wide temperature range. As temperature dependence is not uniform across all the distinct biological processes, acclimation presumably requires complex regulation. The molecular mechanisms that cope with the disruptive effects of temperature variation are still poorly understood. Interestingly, one of five different β-tubulin paralogs, βTub97EF, was among the genes upregulated at low temperature in cultured Drosophila cells. As microtubules are known to be cold sensitive, we analyzed whether βTub97EF protects microtubules at low temperatures. During development at the optimal temperature (25°C), βTub97EF was expressed in a tissue-specific pattern primarily in the gut. There, as well as in hemocytes, expression was increased at low temperature (14°C). Although βTub97EF mutants were viable and fertile at 25°C, their sensitivity within the well-tolerated range was slightly enhanced during embryogenesis specifically at low temperatures. Changing β-tubulin isoform ratios in hemocytes demonstrated that β-Tubulin 97EF has a pronounced microtubule stabilizing effect. Moreover, βTub97EF is required for normal microtubule stability in the gut. These results suggest that βTub97EF upregulation at low temperature contributes to acclimation by stabilizing microtubules.