Source: cnBeta.COM
Millions of years ago, a species of aphid insects called whiteflies incorporated part of a plant's DNA into their genomes. A Chinese research team published an article today (March 25, 2021) in the journal Cell revealing that whiteflies use this stolen gene to degrade common toxins that plants use to defend against insects, allowing whiteflies to safely feed on plants.
"This appears to be the first recorded example of transferring functional genes from the plant level to insects," said co-author Ted Turlings, a chemical ecologist and entomologist at the University of Neuchâtel in Switzerland. "You can't find this gene in any other insect species, BtPMaT1, which neutralizes toxic compounds produced by plants."
Scientists believe that plants may use BtPMaT1 inside their own cells to store their toxic compounds in harmless form so that plants do not poison themselves. Using a combination of genetic and phylogenetic analysis, the team led by Youjun Zhang of the Institute of Vegetables and Flowers of the Chinese Academy of Agricultural Sciences revealed that about 35 million years ago, mealworms stole this defense gene, giving insects the ability to detoxify these compounds for themselves.
"We think a virus inside the plant may have taken up this BtPMaT1 gene, and after being ingested by the whitefly, the virus must have done something inside the insect to integrate the gene into the whitefed genome." Turlings said. "Of course, this is a highly unlikely event, but if you think about the time span of millions of years, billions of individual insects, viruses and plants, it happens occasionally, and if the acquired genes are good for insects, then it will be favored evolutionarily and may spread that advantage."
Mealworms have become the world's leading agricultural pest, capable of attacking at least 600 different species of plants around the world. "One of the questions we've been asking ourselves is how these insects acquired these incredible adaptations to circumvent plant defenses, and with this discovery, we've revealed at least one reason," Turlings said.
Using this knowledge, Turlings' Chinese colleagues created a strategy to undo the superpower of being stolen from the whiteflies. They developed a small RNA molecule that can interfere with the BtPMaT1 gene of whiteflies, making them susceptible to toxic compounds in plants.
"One of the most exciting steps in this design was our colleagues genetically manipulating the tomato plant so that it began to produce this RNA molecule," Turlings said. "Once the whiteflies feed on tomatoes and ingest the RNA produced by the plant, their BtPMaT1 gene goes silent, resulting in 100 percent death of the insect, but this genetic manipulation has no effect on the survival of the other insects tested."
As efforts are focused on producing genetically modified crops that silence the whitefed gene, this could serve as a targeted pest control strategy to combat agricultural damage caused by whitefed populations.
"There are definitely some hurdles to be overcome with this approach, the main one being suspicions about the use of genetically modified plants," he said, "but in the future, I do think this is a very clear way to control whitefly, because now that we know exactly the mechanism behind it, we have the ability to deal with possible changes in the whitefly gene."