Exploring the Ozarks Outdoors: freshare.net

Parasite Modifies Plant to Attract Insects

By Robert J. Korpella

First posted on 11-10-2011


Pathogens can alter their hosts’ behavior, and can also alter the physical characteristics of their hosts. In order to increase its odds of survival into subsequent generations, a viral gene manipulates the behavior of gypsy moth caterpillars to climb trees rather than hide in bark when infected. Malaria parasites have the ability to make humans more appetizing to mosquitoes, thus propagating the illness.

Researchers at the John Innes Centre recently identified a molecule that allows a parasite to influence plant development so that it is more favorable to the insect host.

“Our findings show how this pathogen molecule can reach beyond its host to alter a third organism,” said Dr Saskia Hogenhout from the center.

imageThe team studied leafhoppers, an opportunistic little sap-sucker that pesters people who make a living in agriculture. Beyond the plant damage leafhopper appetites cause, some species also transmit plant pathogens such as viruses and bacteria.

One of these bacteria—called witch’s broom—affects asters, causing the plant to deform into a broom-like appearance as a result of growing multiple stems. The organism depends on leafhoppers for dispersal. But some of the plants that leafhoppers attack emit a chemical response to defend themselves.

The molecule this team isolated reduces the production of specific defense hormones, which allows leafhoppers to lay more eggs and produce more offspring on the host plant. Multiple stems caused by the disease even tend to attract more leafhoppers, since the plant provides more surface area and protection for eggs.

A higher rate of producing offspring likely increases the transmission rate of witch’s broom bacteria through leafhoppers as they travel from plant to plant. The altered plant development gives a distinct competitive advantage to leafhoppers in return for spreading the bacteria.

Photo: A leaf hopper on a finger, watched by Dr. Akiko Sugio and Dr. Saskia Hogenhout. Photo credit: John Innes Centre.

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