On the left the exoskeleton of a normal mosquito larva and on the right a mosquito larva with the gooseberry gene. Photo credit: Alys Jarvela / University of Maryland.
University of Maryland entomologists discovered that mosquitoes lacked a gene that is critical to the survival of other insects – the gene responsible for the proper arrangement of the insect’s segmented bodies. The researchers also found that a related gene evolved to do the job of the missing gene. Although laboratory studies have shown that similar genes can be engineered to replace each other, scientists have for the first time identified a gene that evolved naturally to perform the same critical function as a related gene long after the both genes have gone through different developmental pathways.
The work emphasizes the importance of caution in genetic studies where model animals are used to draw conclusions across species. It also points to a new potential avenue for exploring targeted mosquito control strategies. The research study was published in the journal Communications Biology on September 30, 2020.
“Each and every arthropod has a segmented body plan. And you’d think it would evolve the same for all of them. However, we have found that it doesn’t,” said Alys Jarvela, postdoctoral fellow in the UMD Department of Entomology and lead author the study. “We learn a lot in biology by studying a process in a model organism and assuming that it works in essentially the same way and using the same genes in other organisms. That’s still an incredibly useful approach. But now we know that there is also a possibility for gene substitutions in nature. “
Jarvela accidentally discovered the missing gene in mosquitoes. She studied crickets and tried to check her genetic samples by comparing the genetic sequences of crickets with those of other insects. She was specifically interested in a gene called Paired, one of the few genes that controls the pattern of repeated parts in segmented animals such as insects. Laboratory research had shown that any other segment of the insect’s body would not develop and survive if the pair were knocked out or silenced in fruit flies.
“I was just trying to find the mosquito version of Paired as a reference point and I couldn’t find it,” Jarvela said.
When she searched for pairs of mosquito genomes in all publicly accessible databases, she found that these were missing in every mosquito species represented. “When we accepted that the gene really wasn’t there, we thought that was a pretty wild puzzle and immediately switched gears to satisfy our curiosity,” said Jarvela.
Jarvela’s team searched the genomes of species of flies that are closely related to mosquitoes and found that they all contained the paired gene. This suggested that the loss of pairs is a current evolutionary event that only happened in mosquitoes. It was clear to the researchers that a different gene in mosquitoes had to perform the same function as in other insects.
They found clues as to which gene might be involved in a 1996 experiment on fruit flies. In this study, scientists turned the pair off and replaced them with a closely related gene called gooseberry, which usually plays a special role at a later stage in development. This was a sophisticated experiment, but it showed that fruit flies without the paired gene developed normal alternating segments and survived when gooseberry was manipulated to express at the correct time during development.
To find out if gooseberries evolved naturally to replace pairs of mosquitoes, Jarvela and her team used CRISPR to process gooseberries from a species of mosquito called Anopheles stephensi. The mutated mosquito embryos looked like laboratory fruit fly embryos that had been knocked out.
“This work shows that even when different species share a trait or trait in common, the genetic mechanisms underlying that common trait may be different,” said Leslie Pick, professor and chair of the Department of Entomology at UMD and senior author of the Study. “In the case described in this article, segmentation is still going on, even though a gene we thought was essential is lost. Our next steps will be to look for additional examples of variations in gene regulatory networks in insects and determine where how genetic rewiring occurs nature. “
Jarvela is also interested in studying other aspects of mosquito development that may be affected by loss of the paired gene. In addition to controlling survival segmentation, the pair affects male fertility in fruit flies.
“This means that different genes are likely to regulate male fertility in mosquitoes and may only apply to the mosquito. This could potentially be an effective way to control mosquitoes without harming other insects such as butterflies and bees,” Jarvela said.
The research paper “Regulatory gene function transfer enables essential gene loss in mosquitoes”, Alys M. Cheatle Jarvela, Catherine S. Trelstad and Leslie Pick, was published on September 30, 2020 in the journal Communications Biology.
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Communication Biology (2020). DOI: 10.1038 / s42003-020-01203-w Provided by the University of Maryland
Quote: Mosquitoes lost an essential gene with no negative effects (2020, September 30), found on October 5, 2020 from https://phys.org/news/2020-09-mosquitos-lost-essential-gene-ill.html was retrieved
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