New study uncovers how rice viruses manipulate plant defenses to protect insect vectors

(Press-News.org) Planthoppers and leafhoppers not only feed on rice plants but also act as highly efficient vectors for plant viruses, causing substantial yield losses worldwide. Notably, their persistent ability to evade natural enemies is not merely a matter of chance—it is subtly reinforced by the plant viruses they carry.

A recent study led by Prof. ZHANG Xiaoming's team at the Institute of Zoology of the Chinese Academy of Sciences (CAS), in collaboration with Prof. Ian T. Baldwin's group at the CAS Center for Excellence in Molecular Plant Sciences, has uncovered a novel ecological strategy. Rather than passively "hitchhiking" within insect vectors, rice viruses actively manipulate plant defense pathways to protect their insect carriers. This discovery reshapes our understanding of plant–virus–insect–parasitoid interactions and provides new insights for sustainable pest and pathogen management.

The findings were published in Science Advances on January 7.

Under normal conditions, rice plants respond to attacks by small brown planthoppers and other herbivorous insects by releasing methyl salicylate (MeSA), a volatile organic compound that serves as a chemical distress signal. MeSA not only deters herbivorous insects but also attracts natural enemies such as parasitoid wasps. These wasps lay their eggs inside pest eggs, effectively suppressing pest populations and forming a critical line of indirect plant defense.

However, insect-borne viruses such as Rice Stripe Virus, which is transmitted by small brown planthoppers, can disrupt this defense system. Through their NS2 protein, these viruses suppress MeSA biosynthesis and effectively silence the plant's alarm signal. As a result, parasitoid wasps are no longer recruited, and virus-carrying insects gain effective protection. This creates a self-reinforcing cycle: viruses protect their vectors and vectors in turn facilitate viral transmission.

To break this cycle, the researchers conducted large-scale field experiments over two consecutive years in Jurong, Jiangsu Province. By deploying slow-release MeSA dispensers in rice paddies, they restored the disrupted plant signaling. The results showed that parasitoid wasp abundance increased significantly, pest populations declined, and egg parasitism rates rose from approximately 40% in virus-infected fields to over 60%—matching levels observed in virus-free fields. Meanwhile, viral transmission was effectively suppressed.

As MeSA is a natural metabolite produced by rice plants, this strategy is environmentally friendly, free of chemical pollution, and unlikely to induce resistance. Instead of eliminating pests outright, it restores disrupted ecological interactions and reactivates nature's inherent pest control mechanisms.

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