On the capacity of putative plant odorant-binding proteins to bind volatile plant isoprenoids

Plants use odors not only to recruit other organisms for symbioses, but to talk to each other. Volatile organic compounds (VOCs) from "emitting" plants inform the "receiving" (listening) plants of impending stresses or simply of their presence. However, the receptors that allow receivers to perceive the volatile cue are elusive. Most likely, plants (as animals) have odorant bind proteins (OBPs), and in fact few OBPs are known to bind "stress-induced" plant VOCs. We investigated whether OBPs may bind volatile constitutive and stress-induced isoprenoids, the most emitted plant VOCs, with well-established roles in plant communication. First, we performed a data base search that generated a list of candidate plant OBPs. Second, we investigated in silico the ability of the identified candidate plant OBPs to bind VOCs by molecular simulation experiments. Our results show that monoterpenes can bind the same OBPs that were described to bind other stress-induced VOCs. Whereas, the constitutive hemiterpene isoprene does not bind any investigated OBP and may not have an info-chemical role. We conclude that, as for animal, plant OBPs may bind different VOCs. Despite being generalist and not specialized, plant OBPs may play an important role in allowing plants to eavesdrop messages sent by neighboring plants.