Science - February 14, 2013

Plants prevent fitness loss by caterpillars

Brassica nigra plants accelerate seed production when butterflies drop their eggs on the leaves of the plant. In this way the plants effectively defend themselves against the herbivores, state Wageningen entomologists this week in Functional Ecology.

The Large Cabbage White Butterfly
PhD student Dani Lucas Barbosa studied the responses of Brassica nigra plants to egg deposition by Large Cabbage White butterflies, until the time that the gnawing caterpillars hatching from the eggs were ready to pupate. To her surprise the plants accelerated their seed production before the caterpillar’s eggs had hatched. By the time the eggs had developed to larvae, the flowers were producing seed. As a result, the plants safeguarded their reproductive output, because the larvae do not feed on the seeds that contain high levels of defensive chemicals.
‘We found a new strategy for how plants defend themselves against attackers,’ says research supervisor Joop van Loon. By what means the plants translate leaf surface contact with herbivore eggs to speeding up seed development, is still unknown. Swiss entomologists who collaborate with the Wageningen research group, have found enhanced gene expression of genes in the related plant Arabidopsis thaliana when the plants come into contact with caterpillar’s eggs. ‘Perhaps the information route runs through the vascular system of the plant, or perhaps volatiles give signals that speed up seed production’, says Van Loon.

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