Plant Virus Alters Its Host’s Scent to Attract Bees

Researchers have found that a plant virus changes the scent of tomato plants, attracting more pollinators in the process. The cucumber mosaic virus makes tomato plants smell better to bees, increasing pollination in infected plants. The findings are in a paper just published in the journal PLOS Pathogens.

One of the most common viruses to affect tomato plants is the cucumber mosaic virus (CMV). The virus is transmitted by aphids and results in bitter, misshapen fruit. CMV is one of the most damaging viruses for both cultivated and wild tomato plants.

Researchers from the University of Cambridge conducted an experiment to see how CMV infections affect pollination. They released bumblebees into a flight arena containing a mixture of healthy and infected tomato plants. Interestingly, the bumblebees showed a strong preference for the infected plants. Mass spectrometry analysis provided more clues; emissions from infected plants contained a different mixture of volatiles. Volatiles are chemicals produced by plants that affect scent and can be used to attract pollinating animals. The infected plants emitted a blend of volatiles that was especially attractive to bees.

The researchers discovered that the virus was producing a protein called 2b. The protein altered gene expression in the tomato plants, resulting in the new scent. CMV-infected plants produce less fruit (and therefore less seeds) but the increased pollination from bees might make up for this loss. This may help the virus in two ways. First, the extra pollination will result in new plants that can act as future hosts for the virus. Also, by aiding the plant’s reproduction, the virus might prevent its host from evolving disease resistances.

The results explain why viruses such as CMV can persist for long periods of time, even in wild populations. The researchers hope that their findings can also help increase farmers’ crop yields. If bee-friendly scents are identified, they could be artificially reproduced and sprayed on crops to attract pollinators.

REFERENCE

Simon C. Groen et al. Virus Infection of Plants Alters Pollinator Preference: A Payback for Susceptible Hosts? PLOS Pathogens (2016).

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