Induced defence of pine (Pinus sylvestris) against egg deposition by sawflies: Characterisation of the elicitor

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Egg deposition by herbivorous insects can induce defensive responses in plants. Pine (Pinus sylvestris) changes its terpenoid odour in response to egg deposition by herbivorous pine sawflies. The oviposition-induced pine volatiles attract egg parasitoids killing the eggs, thus protecting pine from damage by sawfly larval feeding. The elicitor of this indirect plant defence induced by insect egg deposition is known to be located in sawfly oviduct secretion which is attaching the eggs to pine needles. The effect of egg deposition on the plant´s volatile pattern can be mimicked by application of isolated oviduct secretion onto (egg-free) pine needles. Treatment of secretion with a protease destroys its inducing activity, thus indicating a proteinaceous character of the elicitor. This project focuses on the isolation and identification of the elicitor present in oviduct secretion of the pine sawfly Diprion pini. Furthermore, we want to gain information on the effect of mating on elicitor activity. Finally, in order to elucidate the sawfly species specificity of this elicitor, we will chemically analyse oviduct secretion of species closely related to D. pini and search for elicitor homologs.