What to do when you’re a plant and your primary insect pollinator also eats your leaves

Relationships are often a complicated mix of good and bad. This reality of life is perfectly exemplified in the liaisons of the tobacco plant and the tobacco hawkmoth. The moth pollinates the plant, which helps the plant thrive. But the moth also lays eggs on the plant leaves, and those eggs produce larvae, which soon devour the plant leaves. To resolve this dilemma in an optimal way, the plant exploits clever chemistry and plant biology, according to a study (Curr. Biol. 2017, DOI: 10.1016/j.cub.2017.03.017). Researchers led by Shuqing Xu of the Max Planck Institute for Chemical Ecology found that the solution comes courtesy of a volatile compound called (E)-α-bergamotene. At night, when the nocturnal moth is out and about, the plant’s flowers release (E)-α-bergamotene. The molecule activates neurons in the insect’s proboscis, inspiring the moth to stay longer at a flower, which increases the likelihood of pollination. During the day, when the adults are resting but the moth’s larvae are actively searching for a hearty meal, production of (E)-α-bergamotene shifts to the plant’s leaves. That switch attracts predators that feed on the larvae and eggs, protecting the plant. By optimally coordinating the timing and location of (E)-α-bergamotene biosynthesis, the plant has evolved a one-compound chemical strategy that improves pollination and defends against herbivores.