Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China.
LPS, Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing, China.
Mol Ecol. 2020 Jul;29(14):2676-2691. doi: 10.1111/mec.15504. Epub 2020 Jun 26.
Aquatic insects are well adapted to freshwater environments, but the molecular basis of these adaptations remains largely unknown. Most firefly species (Coleoptera: Lampyridae) are terrestrial, but the larvae of several species are aquatic. Here, larval and adult transcriptomes from Aquatica leii (freshwater) and Lychnuris praetexta (terrestrial) were generated to test whether the genes associated with metabolic efficiency and morphology have undergone adaptive evolution to fresh water. The aquatic fireflies had a significantly lower ratio of nonsynonymous to synonymous substitutions than the terrestrial insects, indicating a genomewide evolutionary constraint in the aquatic fireflies. We identified 341 fast-evolving genes and 116 positively selected genes in the aquatic fireflies. Of these, 76 genes exhibiting both fast evolution and positive selection were primarily involved in ATP production, energy metabolism and the hypoxia response. We identified 7,271 differentially expressed genes (DEGs) in A. leii (adults versus larvae) and 8,309 DEGs in L. praetexta (adults versus larvae). DEGs specific to the aquatic firefly (n = 1,445) were screened via interspecific comparisons (A. leii versus L. praetexta) and were significantly enriched for genes involved in metabolic efficiency (e.g., ATP production, hypoxia, and immune responses) and certain aspects of morphology (e.g., cuticle chitin, tracheal and compound eye morphology). These results indicate that sequence and expression-level changes in genes associated with both metabolic efficiency and morphological attributes related to the freshwater lifestyle contributed to freshwater adaptation in fireflies. This study provides new insights into the molecular mechanisms of aquatic adaptation in insects.
水生昆虫很好地适应了淡水环境，但这些适应的分子基础在很大程度上仍不清楚。大多数萤火虫物种（鞘翅目：萤科）是陆生的，但有几个物种的幼虫是水生的。在这里，生成了 Aquatica leii（淡水）和 Lychnuris praetexta（陆生）的幼虫和成虫转录组，以测试与代谢效率和形态相关的基因是否已经适应了淡水环境。水生萤火虫的非同义替换与同义替换的比值明显低于陆生昆虫，表明水生萤火虫的基因组在整体上受到进化限制。我们在水生萤火虫中鉴定出 341 个快速进化的基因和 116 个正选择的基因。其中，76 个表现出快速进化和正选择的基因主要参与 ATP 产生、能量代谢和缺氧反应。我们在 A. leii（成虫与幼虫）中鉴定出 7271 个差异表达基因（DEGs），在 L. praetexta（成虫与幼虫）中鉴定出 8309 个 DEGs。通过种间比较（A. leii 与 L. praetexta）筛选出特定于水生萤火虫的差异表达基因（n=1445），这些基因显著富集于与代谢效率（如 ATP 产生、缺氧和免疫反应）和某些形态方面（如表皮几丁质、气管和复眼形态）相关的基因。这些结果表明，与代谢效率和与淡水生活方式相关的形态特征相关的基因的序列和表达水平的变化有助于萤火虫对淡水的适应。本研究为昆虫水生适应的分子机制提供了新的见解。
