Figure 9.

Proposed Model for the Regulation of HGL-DTG Biosynthesis and Effect on Herbivores in N. attenuata.

A simplified biosynthetic pathway is shown for HGL-DTGs from the 17-hydroxygeranylinalool skeleton to the higher molecular weight HGL-DTGs and their mono- and dimalonylated forms. Herbivore attack and larval oral secretions (OS) elicits JA biosynthesis (requiring lox3) and perception (requiring coi1), which strongly regulate malonylation of HGL-DTGs, and JA perception accelerates glycosylation. ppHS may fine-tune JA-mediated malonylation by altering either the perception of JAs or the positive feedback of JAs on their own biosynthesis. The accumulated HGL-DTGs function as a profoundly effective defense against herbivores.