Gene family evolution and salivary gene expression track diet shifts in hemipterans

Aphids draining sap from a rose bush, bedbugs feeding on human blood, assassin bugs skewering prey, and water striders hunting insects on the surface of a pond all belong to a single insect order, Hemiptera. Few groups of animals have reinvented their diets so many times, and a new comparative genomics study published in BMC Genomics suggests that these repeated evolutionary leaps from plant feeding to predation, omnivory, and blood feeding have left a rich and readable signature in the insects’ genomes. By analyzing 27 hemipteran species representing four distinct feeding strategies, a team of researchers from Zhejiang University, the Guangdong Academy of Agricultural Sciences, and Zhejiang A&F University has traced how gene families expand, contract, and disappear as insects switch what they eat, and has begun to map the salivary gland toolkit that makes each feeding style possible.

The research, led by Guilin Luo and Can Zhao, with Qi Fang and Xinhai Ye as corresponding authors, exploits a natural experiment that evolution has run over millions of years. Hemipterans, commonly known as true bugs, feed by piercing tissues and drawing up liquids through specialized mouthparts. That shared mechanical solution, however, sits atop radically different diets: strict phytophagy, carnivory, omnivory that blends animal and plant material, and hematophagy, the blood feeding practiced by notorious disease vectors such as bedbugs and kissing bugs. Because these transitions have occurred independently in multiple lineages, the order offers an ideal model for asking whether evolution repeatedly arrives at the same genetic solutions, or whether it reaches similar functional outcomes through different molecular routes.

To answer that question, the team performed comparative genomic analyses across the 27 species, cataloguing gene families in each genome and identifying which families had expanded, contracted, or been lost entirely along branches of the evolutionary tree where dietary shifts occurred. The scale of the analysis allowed the researchers to connect patterns of gene family evolution directly to changes in feeding biology, rather than inferring adaptation from single species comparisons. The results, the authors report, uncovered extensive genomic changes associated with dietary adaptation, spanning all three modes of gene family change.

One of the most striking findings concerns the relationship between convergence at different levels of biological organization. When the researchers looked at individual gene families, they found limited overlap between the specific families that changed in independently evolving lineages undergoing parallel dietary shifts. At first glance, this might suggest that each lineage solved the same problem in its own way. But when the analysis moved up a level, to the enriched biological processes that those changing gene families feed into, a different picture emerged. Independent lineages showed functional-level convergence: the same categories of biological processes were enriched repeatedly, even when the underlying gene families differed. In other words, evolution appears to converge on functional themes, such as particular aspects of digestion, detoxification, or cellular metabolism, while the specific genes recruited to serve those themes can vary from lineage to lineage.

The study also documented recurrent changes in specific gene families during reverse transitions, cases where lineages shifted from one feeding strategy to another and then back again. These reversals provide some of the strongest evidence linking genomic change to diet, because they act as replicated evolutionary events. If the same gene families expand or contract both when a lineage enters a new diet and when a related lineage reverses course, the changes are unlikely to be random background noise. Identifying such recurrent signatures helps distinguish genuine adaptation from the many genomic changes that accumulate over time for reasons unrelated to feeding.

Beyond the comparative genomics of whole genomes, the team turned to a tissue that sits at the front line of every hemipteran meal: the salivary glands. True bugs rely heavily on saliva to make their feeding strategy work. Plant-feeding species secrete enzymes and other molecules that help break down plant tissues, suppress plant defenses, and keep sap flowing, while predatory and blood-feeding species use salivary secretions to liquefy tissues, disable prey, or prevent blood from clotting. The researchers therefore carried out a comparative transcriptomic analysis of salivary glands across the same set of species, asking what genes are expressed in the glands of plant feeders versus predators, omnivores, and blood feeders.

This analysis identified numerous species-specific genes and gene families whose expression patterns suggest a role in feeding biology. Many of these are genes unique to single species or restricted to particular lineages, which is consistent with the idea that salivary secretions evolve rapidly as insects adapt to new food sources and the defensive responses of their victims, whether plants or animals. The authors are careful about how these results should be interpreted: rather than proving function, the transcriptomic data generate candidate hypotheses. Each species-specific or diet-associated gene now represents a concrete target for future functional validation, in which researchers could silence or knock out the gene and observe the effect on feeding performance.

The technical approach underlying the study reflects the current state of insect genomics. High-quality genome assemblies for dozens of hemipteran species, produced by many research groups over recent years, made it possible to cluster genes into families across species, infer expansions and contractions on the phylogenetic tree, and test whether the timing of those changes coincides with documented shifts in diet. Layering transcriptomic data from salivary glands on top of the genomic framework allowed the team to move from static gene counts to dynamic gene expression, connecting genome content with the biology of actual feeding. Supplementary materials accompanying the paper provide the detailed gene family and expression datasets for other researchers to mine.

The practical implications extend well beyond evolutionary theory. Several of the dietary transitions the study examines involve some of agriculture’s most damaging pests and medicine’s most troublesome vectors. Plant-feeding hemipterans such as aphids, planthoppers, and stink bugs cause enormous crop losses both directly and by transmitting plant viruses, while blood-feeding species transmit human pathogens. If the genomic and salivary gland candidates identified here can be functionally validated, they may reveal vulnerabilities that pesticides or other control strategies could target, for example by interfering with salivary proteins that are essential for feeding but absent from beneficial insects. Conversely, predatory bugs are valuable biological control agents, and understanding the genomic basis of carnivory could inform efforts to enhance their effectiveness in pest management.

Scientifically, the study speaks to a long-running debate about predictability in evolution. The finding of functional-level convergence despite limited gene-level overlap suggests that adaptation operates with some degree of constraint, steering lineages toward similar biological processes, while leaving room for historical contingency in the specific genetic mechanisms recruited. Hemiptera, with its repeated forward and reverse dietary transitions, offers a unusually clean natural laboratory for probing this question. The authors’ conclusion emphasizes that the results provide insights into the dynamic genomic architecture underlying dietary diversification in the order and highlight candidate genes and pathways for future experimental investigation of dietary adaptation mechanisms.

The work was supported by the National Key Research and Development Program of China, the Program of the National Natural Science Foundation of China, the China Agriculture Research System, and several other Chinese research funds. The paper was published as an open-access article, with the early-shared version citable through a permanent DOI ahead of the final Version of Record. Received in December 2025 and accepted in late August 2026, the study arrives at a moment when genomic datasets for insects are expanding rapidly, enabling exactly the kind of multi-species, multi-tissue comparison that was impractical only a few years ago.

What comes next, the researchers indicate, is experimental. The candidate genes and gene families flagged by the comparative analysis, particularly those expressed in salivary glands, now await functional tests in the laboratory. If even a fraction of them prove central to feeding performance, the study will have done what good comparative genomics is meant to do: convert the raw output of genome sequencing into testable hypotheses about how animals remake themselves, at the molecular level, to conquer a new way of eating. For an order of insects that has repeatedly colonized plants, prey, and blood, that molecular playbook may soon be open for reading.