In new research, a team of scientists from Zhejiang University and Vanderbilt University examined horizontal gene transfer — an important evolutionary force shaping prokaryotic and eukaryotic genomes — in high-quality genomes of 218 insect species, including butterflies and moths, and found that they acquired 1,410 genes exhibiting diverse functions via 741 distinct transfers from microbes. The researchers argue that these genes might have been essential for insect evolution by allowing them to develop beneficial traits in mating behavior, nutrition, growth, and adaptation to environmental changes.
Horizontal gene transfer is fairly common between microbes. For example, bacteria use this mechanism to transmit antibiotic-resistance genes between species.
But scientists more recently have been systematically looking at the phenomenon between insects and microbes or plants.
“Previous studies have shown that horizontal gene transfer may have contributed to insect biodiversity, but nobody knew how large a role it plays in this process,” said Dr. Xing-Xing Shen, an evolutionary biologist at Zhejiang University.
“Since there are a lot of high-quality insect genomes available for our analysis, I thought that now is a good time to systematically investigate how prevalent horizontal gene transfer is in insects.”
For their study, Dr. Shen and colleagues gathered 218 high-quality insect genome samples representing 11 of 19 species-rich orders of insects.
With these data, they were able to draw an evolutionary tree, identify out-of-place genes that are more commonly found in non-animal genomes, and examine what factors contribute to the fate of horizontal gene transfer in insects.
“There were horizontal gene transfer events everywhere we looked,” Dr. Shen said.
“However, we don’t know whether these transfers of genes are beneficial to the insects, or even the functions for most of these genes.”
The authors then decided to validate the function of the most prevalent foreign gene without known functions in insects: LOC105383139.
“LOC105383139 was horizontally introduced into nearly all moths and butterflies from a donor in the bacterial genus Listeria,” they said.
“This gene has persisted in the genome since the time of moths’ and butterflies’ common ancestor more than 300 million years ago.”
In diamondback moths, males lacking LOC105383139 courted females significantly less.
“Surprisingly, we saw those moths lacking this gene cannot produce many viable eggs,” said Dr. Jianhua Huang, also from Zhejiang University.
“Then, we found that the gene influences the male courtship behavior.”