Nicotiana attenuata LECTIN RECEPTOR KINASE1 Suppresses the Insect-Mediated Inhibition of Induced Defense Responses during Manduca sexta Herbivory

Abstract

Nicotiana attenuata has the capacity to respond specifically to herbivory by its natural herbivore, Manduca sexta, through the perception of elicitors in larval oral secretions. We demonstrate that Lectin receptor kinase 1 (LecRK1) functions during M. sexta herbivory to suppress the insect-mediated inhibition of jasmonic acid (JA)–induced defense responses. Gene function analysis performed by reducing LecRK1 expression in N. attenuata by both virus-induced gene silencing and inverted repeated RNA interference (ir-lecRK1 plants) revealed that LecRK1 was essential to mount a full defense response against M. sexta folivory; larvae growing on ir-lecRK1 plants were 40 to 100% larger than those growing on wild-type plants. The insect-induced accumulation of nicotine, diterpene-glucosides, and trypsin protease inhibitors, as well as the expression of Thr deaminase, was severalfold reduced in ir-lecRK1 plants compared with the wild type. The accumulation of JA and JA-Ile was unaffected during herbivory in ir-lecRK1 plants; however, salicylic acid (SA) accumulation was increased by twofold. The expression of nahG in ir-lecRK1 plants prevented the increased accumulation of SA and restored the defense response against M. sexta herbivory. The results suggest that LecRK1 inhibits the accumulation of SA during herbivory, although other mechanisms may also be affected.