A pernicious agricultural pest owes some of its achievements to a gene pilfered from its plant host thousands and thousands of a long time back.
The finding, noted today in Cell1, is the very first regarded case in point of a organic gene transfer from a plant to an insect. It also describes one reason why the whitefly Bemisia tabaci is so adept at munching on crops: the gene that it swiped from vegetation permits it to neutralize a toxin that some vegetation make to protect from bugs.
Early perform suggests that inhibiting this gene can render the whiteflies susceptible to the toxin, offering a potential route to combating the pest. “This exposes a system as a result of which we can tip the scales back again in the plant’s favour,” says Andrew Gloss, who scientific tests plant–pest interactions at the University of Chicago in Illinois. “It’s a remarkable example of how learning evolution can advise new methods for applications like crop protection.”
The diminutive whitefly — which is far more carefully associated to aphids than to flies — wreaks agricultural havoc about the entire world. Bemisia tabaci is among the the most damaging plant pests: whiteflies sup sugary sap from hundreds of kinds of plant, all the while excreting a sticky, sweet material termed honeydew that serves as a breeding floor for mould. Whiteflies are also vectors for much more than 100 pathogenic plant viruses.
That some species of whitefly could owe component of their predatory prowess to genes from other organisms is not fully shocking, mainly because genetic thievery is popular in the arms race amongst crops and their pests. In excess of hundreds of thousands of decades, vegetation and bugs alike have borrowed seriously from microbial genomes, from time to time utilizing their freshly obtained genes to build defensive or offensive strategies.
Some insects, these types of as the coffee berry borer (Hypothenemus hampei), have plundered microbial genes to extract additional diet from really hard-to-digest plant mobile partitions2, and a wild relative of wheat has pilfered a fungal gene to fight off a fungal disorder known as head blight3. But plants and insects were being not acknowledged to steal from just about every other ahead of now.
Entomologist Youjun Zhang at the Chinese Academy of Agricultural Sciences in Beijing and his colleagues have been scouring the B. tabaci genome for stolen genes, when they located one particular that appeared to have developed not in other bugs or microbes, but in crops.
Further analyze showed that the gene can transfer a chemical group on to defensive compounds referred to as phenolic glycosides. These compounds are produced by many vegetation, together with tomatoes, to ward off pests. But the modification brought about by the whitefly gene rendered the compounds harmless.
To test the hypothesis, the crew engineered tomato vegetation to generate a double-stranded RNA molecule capable of shutting down expression of the whitefly gene. Nearly all of the whiteflies that subsequently fed on these doctored tomato plants died.
That final result implies a new usually means of concentrating on whiteflies, claims Jonathan Gershenzon, a chemical ecologist at the Max Planck Institute for Chemical Ecology in Jena, Germany. “It delivers an tremendous prospect to be unique,” he states. “You could hold the whiteflies away but not harm beneficial insects this sort of as pollinators.”
Gene transfer in between species can be challenging to establish, suggests research co-creator Ted Turlings, a chemical ecologist at the College of Neuchâtel in Switzerland. To do so, Zhang, Turlings and their colleagues analysed the sequences of equivalent genes in crops, and decided that the whitefly gene was their evolutionary kin. The team also carried out analyses to exhibit that the gene was built-in into the whitefly genome, and was not the result of plant DNA contaminating samples.
The results have been shocking, but convincing, suggests Yannick Pauchet, a molecular entomologist also at the Max Planck Institute for Chemical Ecology. “According to the details they provide, horizontal gene transfer is the most parsimonious clarification,” he states.
But how the whitefly managed to swipe a plant gene is unclear. 1 chance, claims Turlings, is that a virus served as an intermediate, shuttling genetic content from a plant into the whitefly genome.
As scientists sequence more genomes, it is attainable that they’ll uncover extra examples of gene transfer involving plants and animals, suggests Gloss.
“Insects getting the genes from the vegetation themselves is just that very last bit of the arsenal that we hadn’t located nevertheless,” he claims. “In the struggle involving vegetation and their insect pests or pathogens, there are genes being drawn from all about the tree of daily life.”