Herbivory-induced systemic signals are likely evolutionarily conserved in euphyllophytes.

Abstract

Herbivory-induced systemic signaling has been demonstrated in monocots and dicots and is essential for plant defense against insects. However, the nature and evolution of herbivory-induced systemic signals remain unclear. Grafting is widely used for studying systemic signaling; however, grafting between dicot plants from different families is difficult and grafting is impossible for monocots. In this study, taking advantage of dodder s extraordinary capability of parasitizing various plant species, the field dodder (Cuscuta campestris) was employed to pairwise connect phylogenetically very distant plants, ranging from fern to monocot and dicot plants, and whether interplant signaling occurs after simulated herbivory was analyzed. It was found that simulated herbivory-induced systemic signals can be transferred by dodder between a monocot and a dicot plant and even between a fern and a dicot plant, and the plants that received the systemic signals all exhibited elevated defenses. Thus, we inferred that the herbivory-induced systemic signals are likely evolutionally well conserved among vascular plants. Importantly, we also demonstrate that the jasmonate pathway is likely an ancient regulator of the biosynthesis and/or transport of systemic signals in vascular plants. These findings provide new insight into the nature and evolution of systemic signaling.