PBAN regulates sex pheromone biosynthesis by Ca²⁺/CaN/ACC and Ca²⁺/PKC/HK2 signal pathways in Spodoptera litura

Sex pheromones emitted by female moths play important roles in mate attraction. The molecular mechanism underlying pheromone biosynthesis activating neuropeptide (PBAN)-regulated sex pheromone biosynthesis has been well elucidated in many moth species, although this mechanism is species-dependent. Spodoptera litura, an important pest, has caused serious economic losses to agricultural production, yet the mechanism for its sex pheromone biosynthesis has not been fully identified. The present study investigates in detail mechanism underlying PBAN-regulated sex pheromone biosynthesis in S. litura. The transcriptome sequencing of S. litura pheromone glands (PGs) was analysed to identify a serial of candidate genes potentially involved in sex pheromone biosynthesis. Further investigation revealed a bimodal pattern in both sex pheromone release and mating frequency. PBAN was found to regulate sex pheromone biosynthesis via its receptor by using Ca²⁺ as a secondary messenger, as demonstrated by RNA interference and the application of pharmacological inhibitors. Furthermore, PBAN/Ca²⁺ signalling activated calcineurin (CaN) and acetyl-CoA carboxylase (ACC), which mediated sex pheromone biosynthesis in response to PBAN stimulation. Mostly importantly, hexokinase 2 (HK2) was confirmed to be activated by PBAN/PBANR /Ca²⁺/PKC signalling via phosphorylation at two specific sites (ser⁴²³ and ser⁴³⁴ sites of HK2). Overall, our findings shed light on the intricate processes involved in sex pheromone production in S. litura, in which PBAN regulates sex pheromone biosynthesis through PBAN/PBANR/Ca²⁺/CaN/ACC and PBAN/PBANR/Ca²⁺/PKC/HK2 signalling pathways. These insights significantly contribute to our comprehension of the specific mechanisms underlying sex pheromone biosynthesis in this moth species.