Soy and Arabidopsis receptor-like kinases respond to polysaccharide signals from Spodoptera species and mediate herbivore resistance

Plants respond to herbivory by perceiving herbivore danger signal(s) (HDS(s)), including elicitors, that are present in herbivores' oral secretions (OS) and act to induce defense responses. However, little is known about HDS-specific molecules and intracellular signaling. Here we explored soybean receptor-like kinases (RLKs) as candidates that might mediate HDS-associated RLKs' (HAKs') actions in leaves in response to OS extracted from larvae of a generalist herbivore, Spodoptera litura. Fractionation of OS yielded Fr alpha, which consisted of polysaccharides. The GmHAKs composed of their respective homomultimers scarcely interacted with Fr alpha. Moreover, Arabidopsis HAK1 homomultimers interacted with cytoplasmic signaling molecule PBL27, resulting in herbivory resistance, in an ethylene-dependent manner. Altogether, our findings suggest that HAKs are herbivore-specific RLKs mediating HDS-transmitting, intracellular signaling through interaction with PBL27 and the subsequent ethylene signaling for plant defense responses in host plants. Uemura et al. study the mechanism of herbivore resistance in soybean and Arabidopsis. They show that receptor-like kinases (HAK1/2) respond to a polysaccharide in the oral secretions of Spodoptera litura and then interact with PBL27, resulting in an ethylene-dependent herbivore resistance.