Hundreds of millions of years ago, microbes and plants could have given insects an evolutionary advantage by passing genes to them through horizontal gene transfer. In a study published in the journal Cell on July 18, researchers report that more than 1,400 genes belonging to 218 species of insects, including butterflies and moths, come from bacteria, viruses, fungi and plants. The study argues that these genes could have been essential to the evolution of insects by allowing them to develop beneficial traits in mating behavior, nutrition, growth and adaptation to environmental changes.
Horizontal gene transfer (HGT) is quite common between microbes. For example, bacteria use this mechanism to transmit antibiotic resistance genes between species, but more recently scientists have systematically studied the phenomenon between insects and microbes or plants.
“Previous studies have shown that HGT may have contributed to insect biodiversity, but no one knew how important a role it played in this process,” says lead author Xing-Xing Shen, an evolutionary biologist. at Zhejiang University in Hangzhou, China. “Since there are many high-quality insect genomes available for our analysis, I thought the time was right to systematically investigate the prevalence of HGT in insects.”
Shen’s team at Zhejiang University initiated this project in collaboration with Antonis Rokas, an evolutionary biologist at Vanderbilt University, by collecting 218 high-quality insect genome samples representing 11 of the 19 insect orders. species-rich insects. With the data, they were able to draw an evolutionary tree, identify displaced genes more commonly found in non-animal genomes, and examine factors that contribute to the fate of HGT in insects.
“There were HGT events everywhere we looked,” Shen says. “However, we don’t know if these gene transfers are beneficial for insects, or even the functions of most of these genes,” Shen says. He enlisted the help of another expert, Jianhua Huang, who studies insect gene functions at Zhejiang University.
“Shen walked into my office with a list of over 1,400 genes, and we had to decide where to start,” Huang says. The team decided to validate the function of the most prevalent foreign gene with no known functions in insects: LOC105383139.
“This gene was introduced horizontally into almost all moths and butterflies from a donor of the bacterial genus Listeria“, they report in the study, which means that this gene has persisted in the genome since the time of the common ancestor of moths and butterflies more than 300 million years ago.
They decided to remove this ancient gene from diamondback moth, a pest affecting broccoli and cabbage, and observe what kind of functions it has. “Amazingly, we saw that those butterflies lacking this gene cannot produce many viable eggs,” Huang said. “Then we found that the gene influences male courtship behavior.”
The group plans to do more research into the mechanisms underlying how this gene helps insects mate more efficiently and whether it can be exploited as a pest control tool.
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