Aphids act as pawns to spread viruses

Aphids have become the pawns of crop-infecting viruses which influence their host and force them to change in a way that is beneficial to the parasite.

In this example of extended phenotype, these crop-infecting viruses alter plant biochemistry, making it smell and taste unpleasant to the visiting sap-sucking aphids. This repels the insects, causing them to move onto a healthier plant – unwittingly transporting and spreading the virus.

Dr John Carr from the University of Cambridge said the work started almost accidentally: “About five years ago, a student and I noticed that aphids became sick or died when confined on a virus-infected plant.”

“It’s an illustration of how research driven by curiosity can lead to findings that could have a positive impact in the real world – in this case in combating crop-damaging insects and the viruses they transmit,” he added.

Together with researchers at Imperial College London, Carr and his team monitored the effects of a cucumber mosaic virus on host Arabidopsis plants. The virus attacked the plant’s immune system while also altering its biochemistry. This two-pronged attack weakens the plant so that it can’t fight back against its attacker or visiting aphids.

Although aphids initially landed on the plants, they were instantly repelled and moved onto healthier plants – but not before picking up the virus. In this way the virus has ensured the spread of infection would be self-sustaining and highly efficient.

The research, funded by the BBSRC and published in PLOS ONE, could have a significant impact on African agriculture; Carr and his colleagues hope to work with resource-poor farmers by deploying plants to act as aphid-decoys. This will draw the insects away from crucial drops and stop the spread of infection.