Gene transfer might have helped in the development of better traits in mating, nutrition, growth and adaptation
Over the last hundreds of millions of years, microbes and plants have donated more than 1,400 genes to insects, noted a new study.
The acquisition of microbial genes might have provided insects with better survival tools, according to the study published July 18, 2022, in Cell Press Journal.
This might have helped in the development of better traits in mating, nutrition, growth and adaptation to environmental changes, the study noted.
Also read: Climate change triggering global collapse in insect numbers
The transfer of genes from microbes to insects could have occurred through horizontal gene transfer (HGT). It allows genes to move between different species. Different bacterial species can exchange genes, including antibiotic-resistant ones, through HGT.
“HGT is quite common in bacteria (which are prokaryotes, ie, organisms without a nucleus), but its occurrence in eukaryotes (organisms with a nucleus) has been much more rarely observed,” Antonis Rokas, an evolutionary biologist at Vanderbilt University, told Down To Earth.
We systematically examined the evidence for HGT across insects as they are known to interact with numerous microbes and plants, he added.
The scientists evaluated the evolutionary history of insect genes to understand the prevalence of gene transfer between microbes and insects.
The team analysed insect genome data, collecting 3 million genes from 218 genome samples.
These samples represented 11 insect orders. For example, the order Lepidoptera includes butterflies and moths, while the order Diptera represents mosquitoes, fruit flies, sand flies, blowflies and the House Fly.
Insect genes with microbial origin will be more closely related to genes from bacteria, plants, or fungi than to insects, Rokas said.
Their analysis showed that 1,410 genes from insects could be traced back to microbes. Of these, 1,115 were from bacteria, 194 from fungi, 43 from plants, 36 from viruses and 22 from other lineages.
Some insect orders acquired more genes than others. Lepidoptera acquired the lion’s share, followed by the Hemiptera (cicadas, aphids and bed bugs), Coleoptera (beetles and weevils), Hymenoptera (wasps, bees, and ants), and Diptera.
“It is possible that some of the observed differences come down to differences in the species’ ecologies,” Rokas said, adding that scientists are yet to understand it.
Next, the team zeroed in on one gene, ‘LOC105383139 ’, of the 1,410 to investigate its function in insects. LOC105383139 gene is present in nearly all moths and butterflies.
The donor of this gene appears to be the bacterial genus Listeria. Two species belonging to this genus act as parasites in mammals.
The function of LOC105383139, however, was unknown, Rokas highlighted. To study that, the team removed the gene in diamondback moths, a serious agricultural pest of broccoli and cabbage.
“Surprisingly, we saw those moths lacking this gene cannot produce many viable eggs,” Jianhua Huang, who studies insect gene functions at Zhejiang University, said in a statement.
The experiment showed that the gene plays a role in male courtship behaviour, the study stated. However, the researchers do not rule out the possibility that some HGT-acquired genes could be harmful.
“We do not know that all 1,410 genes that we identified are actually advantageous to their insect hosts,” Rokas stressed.
The acquisition of foreign DNA by an organism, he explained, can often be a disadvantage. Organisms with a piece of bad foreign DNA don’t survive and reproduce as often as organisms without it, he said.
Alternatively, some genes acquired through HGT, Rokas added, can also be neutral, neither beneficial nor harmful. The team hopes to work out the functions of each gene in their further studies.
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