In the evolutionary history of insects, “foreign patents” apparently played an important role: researchers have identified genes in the genome of many insect species that their ancestors once received through horizontal gene transfer. They came primarily from bacteria, but also from fungi, viruses and plants. According to the study, these special hereditary factors apparently fulfill important functions in insects: With one of the genes, the scientists were able to show an importance for the mating behavior of a moth species.
The transfer of genetic material from one species to another is mostly associated with genetic engineering. But this process also occurs naturally. In microbes, this so-called horizontal gene transfer is very common. In this way, different types of bacteria mediate resistance to antibiotics, for example. In contrast, transfers of genetic information from microbes or other organisms to animals are extremely rare. However, they did occur in the course of evolutionary history, as studies have already shown: Researchers have already identified genes in the genome of insects that, according to their characteristics, originally came from microbes or plants. However, the extent and importance of horizontal gene transfer in the evolutionary history of insects is still unknown.
On the trail of acquired genes
The team led by Xing-Xing Shen from the Chinese Zhejiang University in Hangzhou has now dealt with this research topic. “With many high-quality insect genomes now available for analysis, we thought this would be a good time to systematically examine how common traces of horizontal gene transfer are in insects,” says Shen. As part of the study, he and his colleagues analyzed 218 genomes of insects from particularly species-rich groups. Using certain genetic characteristics, they were able to track down the “foreign” genes in their genome and obtain information as to when and from which creatures they were once transmitted.
“Everywhere we looked, we found traces of horizontal gene transfer,” reports Shen. In total, the scientists found 1,410 genes in the genomes they examined that once got into the insect genomes from non-animal donors. Most of them could be traced back to bacteria based on their genetic characteristics. However, some of the non-insect genes also came from fungi, viruses and plants. The scientists report that insects from the group of butterflies (Lepidoptera) have acquired a particularly large number of foreign hereditary factors in the course of their evolutionary history.
Foreign genes with meaning
It is obvious that the genetic transfers were able to give the recipients great advantages by suddenly giving them new characteristics. Among other things, the immune system, metabolism, fertility and the ability to adapt to various environmental factors may have benefited. As part of the study, the researchers also looked into the function of one of the identified genes: It was the fairly widespread foreign gene LOC105383139, of which there was no indication of its function. According to the genetic characteristics, it came from a donor from the bacterial genus Listeria. Today it is found in the genome of almost all butterflies and moths. This means that this gene has been preserved in the genome since a horizontal transfer to the common ancestor of moths and butterflies more than 300 million years ago, the researchers explain.
In order to track down its function, they removed LOC105383139 using Crispr/Cas9 gene scissors from the genome of a “model butterfly” that is known to be a pest on crops: the diamond-back moth (Plutella xylostella). The investigations of this breeding line subsequently revealed: The moths, which lack the gene, produced significantly fewer offspring. “Then we found out that the gene influences the courtship behavior of the males,” reports Huang. The hereditary disposition, once transmitted by horizontal gene transfer from bacteria, apparently acquired a function in mating behavior in the ancestors of the butterflies.
With the proof of the function of this one gene, the researchers have already made an interesting finding, because it may have practical application potential: information about the meaning of LOC105383139 could lead to the development of novel agents for pest control. That’s why the researchers are now planning to take a closer look at how this “special” gene helps the insects to mate more effectively.
Source: Cell Press, Article: Cell, doi: 10.1016/j.cell.2022.06.014