Insects Rewired an Ancient Sugar Enzyme to Power Their Evolutionary Success

Trehalose is, for many insects, what glucose is for humans: the circulating sugar that fuels flight, growth, metamorphosis, and survival through harsh conditions. The enzyme that breaks it down, trehalase, has long been treated as a textbook example of a conserved metabolic workhorse. A new study published in BMC Biology shows that this apparent simplicity hides a far more dynamic evolutionary story, one in which insects repeatedly multiplied and retooled their trehalase genes while vertebrates largely kept a single copy.

The research, led by Yanyan Zhou and Huabing Wang of Zhejiang University together with colleagues, set out to answer a deceptively simple question in evolutionary biology: how do conserved metabolic pathways diversify to support lineage-specific physiological adaptation? To find out, the team carried out one of the broadest surveys of trehalase evolution to date, examining 808 animal genomes for the presence, absence, duplication, and deterioration of trehalase genes, and then followed up with functional experiments in the silkworm, Bombyx mori.

The comparative results revealed a striking asymmetry between the two great branches of the animal kingdom. In vertebrates, the trehalase gene, known as Treh, was predominantly retained as a single copy, although in some species it appears to have been lost outright or reduced to a non-functional pseudogene. Insects, by contrast, underwent recurrent expansion of their trehalase repertoire, suggesting that the demands of insect physiology have repeatedly favored extra copies of this sugar-cleaving enzyme.

That expansion was not spread evenly across the trehalase family. Insects carry two main trehalase types, Treh1 and Treh2, and the gene duplication events were concentrated almost entirely in Treh1, particularly within three of the most species-rich insect orders: the Hemiptera, or true bugs; the Coleoptera, or beetles; and the Lepidoptera, the order of moths and butterflies that includes the silkworm. Treh2, meanwhile, almost always remained a single-copy gene, hinting that the two enzyme types perform fundamentally different roles that constrain how many copies each can tolerate.

One of the most intriguing patterns emerged in the Lepidoptera, which consistently retained a conserved tandem pair of Treh1 paralogs, designated Treh1a and Treh1b, sitting side by side in the genome. Tandem duplication of this kind is a classic route to functional divergence: once two copies exist, one is freed from the full burden of maintaining the ancestral function and can accumulate mutations that shift its expression pattern, substrate preference, or tissue specificity. The persistence of this pair across moths and butterflies suggests it has been maintained by natural selection rather than random drift.

To test whether these paralogs actually do different jobs, the researchers turned to CRISPR-Cas9 genome editing in Bombyx mori, the domesticated silkworm and a long-standing model for insect physiology. They disrupted each paralog in turn, generating mutants lacking functional Treh1a and mutants lacking functional Treh1b, and then measured the consequences for growth, enzyme activity, gene expression, and metabolism.

Both mutant lines showed reduced adult body mass and reduced trehalase activity, confirming that each paralog contributes measurably to the total capacity of the animal to break down trehalose. But the diet of the developing larvae revealed a subtler picture: lower larval body weights were observed when the insects were reared on an artificial diet, yet not when they fed on fresh mulberry leaves, their natural food. This diet-dependent effect suggests that the trehalase paralogs become especially important under nutritional conditions that differ from the insect’s evolved feeding environment, a finding with clear implications for laboratory studies and for pest species that encounter varied food sources in the field.

Transcriptomic and metabolomic profiling of the mutants deepened the story. By sequencing messenger RNA and measuring metabolite levels across wild-type and mutant animals, the team uncovered both shared responses and genotype-specific ones. In other words, losing Treh1a and losing Treh1b do not simply subtract the same amount of enzyme activity; each loss sends the insect’s metabolic and transcriptional networks down partly distinct paths of compensation and disruption. The paralogs overlap in function, but they are not interchangeable, exactly the signature expected of genes that duplicated and then diverged in their physiological roles.

The broader significance of the work lies in the framework it provides. By combining a survey of hundreds of animal genomes with targeted functional genetics in a single model species, the study connects a large-scale evolutionary pattern, the Treh1-biased expansion of trehalase in insects, to concrete physiological consequences measurable in the laboratory. It offers a comparative and functional foundation for understanding why trehalose metabolism, so stable in vertebrates, became a site of evolutionary experimentation in insects.

There are practical stakes as well. Trehalase is already a target of interest in agricultural pest control, because blocking trehalose breakdown disrupts energy supply in insects without directly affecting vertebrates, which rely on glucose instead. The new findings suggest that pest control strategies may need to account for which trehalase paralogs a given species carries and how those paralogs partition their duties. For the many beetle, bug, and moth species that have expanded their Treh1 complements, a single-enzyme inhibitor may not be enough, and the diet-dependent growth effects observed in the silkworm hint that the effectiveness of such interventions could vary with the food environment. As genomes from more animal species accumulate, the picture painted by this study, of a quiet enzyme family shaped by repeated duplication and divergence, is likely to become an increasingly important lens for understanding how metabolism itself evolves.

Subject of Research: Evolutionary expansion and functional divergence of trehalase genes in insect trehalose metabolism

Article Title: Trehalase expansion and functional divergence in the evolution of insect trehalose metabolism

Article References: Trehalase expansion and functional divergence in the evolution of insect trehalose metabolism. (n.d.). https://doi.org/10.1186/s12915-026-02764-8

Image Credits: AI Generated

DOI: 10.1186/s12915-026-02764-8

Keywords: trehalase, trehalose metabolism, insects, gene duplication, molecular evolution, Bombyx mori, CRISPR-Cas9, functional diversification, metabolic adaptation, Lepidoptera, Treh1, genomics