Bosshardt, F. | Search bioRxiv

bioRxiv2020

A cis-regulatory element promoting increased transcription at low temperature in cultured ectothermic Drosophila cells

Cells of many ectothermic species, including Drosophila melanogaster, maintain homeostatic function within a considerable temperature range. The cellular mechanisms enabling temperature acclimation are still poorly understood. At the transcriptional level, the heat shock response has been extensively analyzed. The opposite has received less attention. Here, using cultured Drosophila cells, we have identified genes with increased transcript levels at the lower end of the readily tolerated temperature range, as well as chromatin regions with increased DNA accessibility. Candidate cis-regulatory elements (CREs) for transcriptional upregulation at low temperature were selected and evaluated with a novel reporter assay for accurate assessment of their temperature-dependency. Robust transcriptional upregulation at low temperature could be demonstrated for a fragment from the pastrel gene, which expresses more transcript and protein at reduced temperatures. The CRE is controlled by the JAK/STAT signaling pathway and antagonizing activities of the transcription factors Pointed and Ets97D.

cell biology↗

bioRxiv2017

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

Summary statementEctotherms thrive within an often remarkable temperature range. At low temperature, betaTub97EF, a beta-tubulin paralog stabilizing microtubules, is upregulated in a tissue-specific manner in the fly Drosophila melanogaster.\n\nAbstractCells 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 coping with the disruptive effects of temperature variation are still poorly understood. Interestingly, one of five different beta-tubulin paralogs, betaTub97EF, was among the genes up-regulated at low temperature in cultured Drosophila cells. As microtubules are known to be cold-sensitive, we analyzed whether betaTub97EF protects microtubules at low temperatures. During development at the optimal temperature (25{degrees}C), betaTub97EF was expressed in a tissue-specific pattern primarily in the gut. There, as well as in hemocytes, expression was increased at low temperature (14{degrees}C). While betaTub97EF mutants were viable and fertile at 25{degrees}C, their sensitivity within the well-tolerated range was slightly enhanced during embryogenesis specifically at low temperatures. Changing beta-tubulin isoform ratios in hemocytes demonstrated that beta-Tubulin 97EF has a pronounced microtubule stabilizing effect. Moreover, betaTub97EF is required for normal microtubule stability in the gut. These results suggest that betaTub97EF up-regulation at low temperature contributes to acclimation by stabilizing microtubules.

developmental biology↗