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Tobacco: actually pretty bad food for leafhoppers
Empoasca sp. is not a typical pest of wild tobacco (Nicotiana attenuata). When this plant grows in its natural habitats in North America, however, it is attacked by tobacco hornworm larvae (Manduca sexta). This specialist insect is resistant to the toxic nicotine, which the plant produces as a defense against its enemies. When researchers from the Max Planck Institute for Chemical Ecology used particular transgenic plants in field experiments, they noticed that these plants were heavily infested with Empoasca leafhoppers in comparison to wild-type plants. In the particular transgenic plants used in this study, a certain gene, lox3, had been switched off which is essential for the production of jasmonic acid. Due to their inability to produce jasmonates, the plants could not activate their defenses against herbivores, because their hormonal signaling cascades were interrupted. The result of this deficiency was visible and had been expected: a heavy infestation by tobacco hornworm larvae. The occurrence of leafhoppers, however, was a surprise, because these insects are not a part of the plant's normal herbivore community. The scientists speculated that these insects which are common pests of agricultural crops may have been able to evaluate the defensive potential of their host plants before the plants could activate the production of their defenses.
Leafhoppers evaluate jasmonate-based signaling
To test this hypothesis, the scientists produced different transgenic tobacco lines and used them in field experiments. In six lines, the expression of specific enzymes involved in jasmonate production was blocked or the perception of the jasmonate signal was inhibited, and in three lines the production of jasmonate-elicited to
|Contact: Ian T. Baldwin|
Max Planck Institute for Chemical Ecology