Altered Octopamine synthesis impairs tyrosine metabolism affecting Helicoverpa armigera vitality

Abstract

Tyramine β-hydroxylase (TβH) is a key enzyme in the biosynthesis of octopamine (OA), a vital neurohormone in invertebrates. This study explores the expression patterns and functional role of Helicoverpa armigera TβH (HaTβH) across various tissues and developmental stages. HaTβH expression was highest in the head and adult male stages, reflecting tissue-specific and developmental regulation. HaTβH silencing significantly increased locomotion and decreased feeding behavior. OA supplementation in silenced insects or HaTβH overexpression showed a contrary effect on locomotory and feeding behavior. In silico screening and inhibitory assays identified tomatidine, a tomato-derived metabolite, as a potent HaTβH inhibitor with strong binding affinity. In vivo bioassays confirmed tomatidine's inhibitory effects, reducing feeding and increasing mortality in H. armigera. Modulation in HaTβH expression or activity disturbs the tyrosine metabolic pathway, with altered levels of tyramine, octopamine, and dopamine. These results highlight HaTβH as a key regulator of OA biosynthesis, influencing insect feeding, locomotion, and overall survival. The present study also introduces tomatidine as a potential candidate for insect control, given its ability to disrupt HaTβH function. This work provides new insights into the physiological roles of HaTβH and offers promising avenues for developing targeted pest management strategies.