The silver white fly (Bemisia tabaci) introduced a gene called BtPMaT1 from plants into their genome about 35 million years ago and is now using it to neutralize toxins that plants use to protect themselves against insects, allowing the butterfly to feed the plants safely.
Silverleaf White Flies (Bemisia tabaci) phenolic glucoside maltyltransferase BtPMaT1 malonyltransferase gene expression, which enables the insecticides to neutralize phenolic glycosides in host plants. Image credit: Xia et al., doi: 10.1016 / j.cell.2021.02.014.
Plants defend themselves with a wide range of toxic compounds, but most plants are food for insects.
Most of the evolutionary processes that allow fungal insecticides to protect against plants are unknown.
The silver white pupae is a cosmopolitan agricultural pest that attacks at least 600 different species of plants worldwide.
This insect also protects against a number of pathogenic viruses of plants and is an excellent model for studying the molecular mechanisms involved in overcoming plant immunity.
“This appears to be the first recorded example of a horizontal gene transfer of active gene from plant to beast,” said Dr. Ted Turlings, a researcher at the University of Neuchâtel.
“You can’t find this gene, BtPMaT1, which neutralizes plant-produced toxic fertilizers in any other insect species. ”
“Plants may use BtPMaT1 in their own cells to store their toxic fertilizers in a harmless form, so the plant will not poison itself. ”
Dr Turlings and his colleagues used a combination of genetic and phylogenetic analyzes, to reveal that silver white flies stole this protective gene 35 million years ago, enabling the beast to disinfect these fertilizers. yourself.
“We believe that a virus inside the plant may have absorbed the BtPMaT1 gene and, after being ingested by a white fly, the virus then needs something to infect it. inside the insect with which that gene was incorporated into the whitefly genome, ”said Dr Turlings.
“Of course, this is a very unlikely event, but if you think about millions of years and billions of individual insects, viruses and plants over time, this could happen once, and if the gene which has been found to benefit the insects, then favors evolution and can spread. ”
“One of the questions we have been asking ourselves is how did these insects get these amazing changes to get around plant defenses, and with this discovery we have at least show one reason why, ”he said.
The researchers developed a small RNA molecule that inhibits the BtPMaT1 gene of the white flies, making the white flies susceptible to the plant’s toxic compounds.
“The most exciting step of this design was when our colleagues manipulated tomato plants genetically to begin producing this RNA molecule,” said Dr. Turlings.
“As soon as the whiteflies fed the tomatoes and absorbed the plant-produced RNA, their BtPMaT1 gene was silenced, causing 100% death of the insect, but the genetic treatment has no effect on the survival of other proven insecticides. ”
The findings appear in the journal Cell.
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Jixing Xia et al. Whitefly carries a plant detoxification gene that neutralizes plant toxins. Cell, published online March 25, 2021; doi: 10.1016 / j.cell.2021.02.014