In a new study published by Cell Press, experts are explaining why whiteflies incorporated a portion of plant DNA into their genome millions of years ago. The researchers have discovered that whiteflies use the stolen gene to degrade the toxins that plants use to defend themselves against insects.
Study co-author Ted Turlings is a chemical ecologist and entomologist at the University of Neuchâtel in Switzerland.
“This seems to be the first recorded example of the horizontal gene transfer of a functional gene from a plant into an insect,” said Turlings. “You cannot find this gene, BtPMaT1, which neutralizes toxic compounds produced by the plant, in any other insect species.”
Experts theorize that plants use BtPMaT1 to store their noxious compounds in a harmless form so that the plant does not poison itself.
The research team, led by Youjun Zhang of the Chinese Academy of Agricultural Sciences, used genetic analyses to reveal that whiteflies stole BtPMaT1 about 35 million years ago. The flies then gained the ability to detoxify toxic plant defense compounds.
“We think a virus within the plant may have taken up this BtPMaT1 gene and, after ingestion by a whitefly, the virus then must have done something inside the insect whereby that gene was integrated into the whiteflies genome,” explained Turlings.
“Of course, this is an extremely unlikely event, but if you think about millions of years and billions of individual insects, viruses, and plants across time, once in a while this could happen, and if the acquired gene is a benefit to the insects, then it will be evolutionarily favored and may spread.”
Whiteflies are a major agricultural pest, attacking at least 600 different species of plants worldwide.
“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 have revealed at least one reason as to why,” said Turlings.
Based on the findings, the team developed a small RNA molecule that interferes with the whiteflies’ BtPMaT1 gene and makes the flies susceptible to the plant’s toxic compounds.
“The most exciting step of this design was when our colleagues genetically manipulated tomato plants to start producing this RNA molecule,” said Turlings.
“Once the whiteflies fed on the tomatoes and ingested the plant-produced RNA, their BtPMaT1 gene was silenced, causing 100% mortality of the insect, but the genetic manipulation had no impact on the survival of other insects that were tested.”
Silencing the whitefly gene could serve as a targeted pest control strategy to combat agricultural devastation caused by whiteflies.
“There are definitely still some hurdles this method needs to get over, most notably the skepticism about using transgenic plants,” said Turlings.
“But in the future, I do see this as a very clear way of controlling whiteflies because now we know exactly the mechanism behind it, and we are equipped to deal with possible changes in the whitefly gene that may arise.”
The study is published in the journal Cell.
By Chrissy Sexton, Earth.com Staff Writer