IBMC-Instituto de Biologia Celular e Molecular, University of Porto, Porto, Portugal.
PLoS One. 2011;6(10):e25520. doi: 10.1371/journal.pone.0025520. Epub 2011 Oct 3.
The molecular basis of short term cold resistance (indexed as chill-coma recovery time) has been mostly addressed in D. melanogaster, where candidate genes (Dca (also known as smp-30) and Frost (Fst)) have been identified. Nevertheless, in Drosophila, the ability to tolerate short term exposure to low temperatures evolved several times independently. Therefore, it is unclear whether variation in the same candidate genes is also responsible for short term cold resistance in distantly related Drosophila species. It should be noted that Dca is a candidate gene for cold resistance in the Sophophora subgenus only, since there is no orthologous gene copy in the Drosophila subgenus. Here we show that, in D. americana (Drosophila subgenus), there is a north-south gradient for a variant at the 5' non-coding region of regucalcin (a Dca-like gene; in D. melanogaster the proteins encoded by the two genes share 71.9% amino acid identities) but in our D. americana F2 association experiment there is no association between this polymorphism and chill-coma recovery times. Moreover, we found no convincing evidence that this gene is up-regulated after cold shock in both D. americana and D. melanogaster. Size variation in the Fst PEST domain (putatively involved in rapid protein degradation) is observed when comparing distantly related Drosophila species, and is associated with short term cold resistance differences in D. americana. Nevertheless, this effect is likely through body size variation. Moreover, we show that, even at two hours after cold shock, when up-regulation of this gene is maximal in D. melanogaster (about 48 fold expression change), in D. americana this gene is only moderately up-regulated (about 3 fold expression change). Our work thus shows that there are important differences regarding the molecular basis of cold resistance in distantly related Drosophila species.
短期抗寒（以冷休克昏迷恢复时间为指标）的分子基础在黑腹果蝇中已得到广泛研究，其中候选基因（Dca（也称为 smp-30）和 Frost（Fst））已被鉴定。然而，在果蝇中，短期耐受低温的能力已经独立进化了多次。因此，在亲缘关系较远的果蝇物种中，相同候选基因的变异是否也与短期抗寒能力有关尚不清楚。值得注意的是，Dca 只是 Sophophora 亚属的抗寒候选基因，因为在 Drosophila 亚属中没有其直系同源基因。在这里，我们表明，在 D. americana（果蝇亚属）中，在 regucalcin（Dca 样基因的 5'非编码区存在一个南北梯度；在 D. melanogaster 中，这两个基因编码的蛋白质具有 71.9%的氨基酸同一性），但在我们的 D. americana F2 关联实验中，这种多态性与冷休克昏迷恢复时间之间没有关联。此外，我们没有发现令人信服的证据表明，在 D. americana 和 D. melanogaster 中，该基因在冷休克后会被上调。当比较亲缘关系较远的果蝇物种时，会观察到 Fst PEST 结构域（可能参与快速蛋白降解）的大小变异，并且与 D. americana 的短期抗寒差异相关。然而，这种影响可能是通过体型的变化。此外，我们表明，即使在冷休克后两小时，当 D. melanogaster 中该基因的上调达到最大值（约 48 倍的表达变化）时，在 D. americana 中，该基因仅适度上调（约 3 倍的表达变化）。因此，我们的工作表明，在亲缘关系较远的果蝇物种中，抗寒的分子基础存在重要差异。
