Annals of Botany

Terpenoid transfer across mycorrhizal networks strengthens host plant resistance

Plants, though sessile, employ various strategies to defend themselves against herbivorous insects. The production of terpenoids, and formation of symbiotic associations with arbuscular mycorrhizal fungi (AM) are two such defensive strategies.

Overview of terpenoids in plant defence against herbivorous insects.
Overview of terpenoids in plant defence against herbivorous insects. Volatile terpenoids that belong to the HIPVs (herbivore-induced plant volatiles) and OIPVs (oviposition-induced plant volatiles) are released in response to herbivore attack and oviposition, respectively. Terpenoids induce defence responses in the systemic parts of the same plant. These volatiles attract insect carnivores that feed on the herbivores, thereby inducing indirect defence in plants, and prime neighbouring conspecific and heterospecific plants. The perception of terpenoids by neighbouring plants results in influx of calcium ions and membrane depolarization. Epigenetic regulation of this priming response is reported to evoke the priming memory for up to 5 d. Terpenoids also affect tritrophic interactions in soil.

Terpenoids deter herbivores, attract their predators and serve as airborne signals that induce defence responses in neighbouring uninfested plants. Sharma et al. show that AM affect the concentration and composition of terpenoids, boosting defence against herbivores. Hyphal networks in soil serve as conduits facilitating the transfer of defence signals and terpenoids between plants. Improved understanding of terpenoids and AM in plant defence will have significant implications for sustainable pest management in agricultural ecosystems.

This paper is part of the Annals of Botany Special Issue on Plant Immunity. It will be free access till June 2017 and after April 2018.

Reference

Sharma, E., Anand, G., & Kapoor, R. (2017). Terpenoids in plant and arbuscular mycorrhiza-reinforced defence against herbivorous insects. Annals of Botany, mcw263. https://doi.org/10.1093/aob/mcw263