Gene duplication provides a major source of new genes for evolutionary novelty and ecological adaptation. However, the maintenance of duplicated genes and their relevance to adaptive evolution has long been debated. Insect trehalase (Treh) plays key roles in energy metabolism, growth, and stress recovery. Here, we show that the duplication of Treh in Lepidoptera (butterflies and moths) is linked with their adaptation to various environmental stresses. Generally, two Treh genes are present in insects: Treh1 and Treh2. We report three distinct forms of Treh in lepidopteran insects, where Treh1 was duplicated into two gene clusters (Treh1a and Treh1b). These gene clusters differ in gene expression patterns, enzymatic properties, and subcellular localizations, suggesting that the enzymes probably underwent sub- and/or neofunctionalization in the lepidopteran insects. Interestingly, selective pressure analysis provided significant evidence of positive selection on duplicate Treh1b gene in lepidopteran insect lineages. Most positively selected sites were located in the alpha-helical region, and several sites were close to the trehalose binding and catalytic sites. Subcellular adaptation of duplicate Treh1b driven by positive selection appears to have occurred as a result of selected changes in specific sequences, allowing for rapid reprogramming of duplicated Treh during evolution. Our results suggest that gene duplication of Treh and subsequent functional diversification could increase the survival rate of lepidopteran insects through various regulations of intracellular trehalose levels, facilitating their adaptation to diverse habitats. This study provides evidence regarding the mechanism by which gene family expansion can contribute to species adaptation through gene duplication and subsequent functional diversification.

中文翻译：

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海藻糖酶的复制和多样化赋予鳞翅目昆虫进化优势。

基因复制为进化的新颖性和生态适应性提供了新基因的主要来源。但是，重复基因的维持及其与适应性进化的相关性一直存在争议。海藻糖酶（Treh）在能量代谢，生长和压力恢复中起关键作用。在这里，我们表明Treh在鳞翅目（蝴蝶和飞蛾）中的复制与它们对各种环境压力的适应性相关。通常，昆虫中存在两个Treh基因：Treh1和Treh2。我们报告了鳞翅目昆虫中Treh的三种不同形式，其中Treh1被复制成两个基因簇（Treh1a和Treh1b）。这些基因簇在基因表达方式，酶学性质和亚细胞定位方面存在差异，提示该酶可能在鳞翅目昆虫中经历了亚功能和/或新功能。有趣的是，选择性压力分析为鳞翅目昆虫谱系中重复的Treh1b基因的阳性选择提供了重要的证据。最积极选择的位点位于α-螺旋区域，几个位点靠近海藻糖结合位点和催化位点。由于特定序列的选定变化，似乎已发生由阳性选择驱动的重复Treh1b的亚细胞适应，从而允许在进化过程中对重复的Treh1b进行快速重编程。我们的研究结果表明，通过不同的细胞内海藻糖水平调控，Treh的基因复制和随后的功能多样化可以提高鳞翅目昆虫的存活率，促进它们适应各种生境。这项研究提供了有关基因家族扩展可通过基因复制和随后的功能多样化促进物种适应的机制的证据。