Stem parasitic plant Cuscuta australis (dodder) transfers herbivory-induced signals among plants

Significance Cuscuta spp. (i.e., dodders) are plant parasites that connect to the vasculature of their host plants to extract water, nutrients, and even macromolecules. Knowledge of ecologically meaningful communications between host plants and Cuscuta , or between Cuscuta bridge-connected hosts, has remained obscure until now. Here we show that herbivore attack on one of the Cuscuta bridge-connected plants induces gene expression and increases the activity of trypsin proteinase inhibitors, and thus elevates the resistance to insects in other undamaged but Cuscuta -connected plants. This Cuscuta -mediated interplant signaling is rapid, conserved, far-reaching, and partly requires the plant hormone jasmonic acid. Although Cuscuta parasites can negatively influence their host plants, under certain circumstances, they may also provide ecologically relevant information-based benefits.