WHEN SOME plants are attacked by herbivores they fight back by producing irritants and toxins as their leaves get chewed up. Certain insects, however, can resist these defences. Among the best at doing this, and hence one of the most troublesome crop pests, is the whitefly. Remarkably, as new research shows, whiteflies enhance their dastardly deeds by hacking a biological early-warning communications system used by plants.
When whiteflies launch an attack, plants respond by producing jasmonic acid as a defence mechanism. This hormone triggers the production of compounds that interfere with an insect’s digestive enzymes, making it difficult for them to feed. But plants can produce a different substance, salicylic acid, to help ward off pathogens, such as a virus. Whiteflies trick the plant into behaving as if it was threatened with a disease rather than an insect infestation. This is possible because whiteflies have compounds in their saliva that dupe plants into producing more salicylic acid and less insect-repelling jasmonic acid. This ruse makes it much easier for them to infest the plant.
Raising the alarm
Peng-Jun Zhang and Xiao-Ping Yu of Jiliang University in China, and their colleagues, wondered whether there might be more to it than that. In particular they decided to investigate what...