Supplemental Sugar Is Required for Sex Pheromone Biosynthesis in Mythimna separata

Abstract

Supplemental nutrients of adult moths maximize moth fitness and contribute to the pollination of many plants. Previous reports have revealed that sugar feeding promotes to sex pheromone biosynthesis by increasing the haemolymph trehalose concentration in mating moths. Here, Mythimna separata adults were employed as a model to investigate the effect of sugar feeding on sex pheromone biosynthesis. Results showed that in virgin females, sugar feeding markedly increased the concentrations of trehalose, pyruvic acid, and acyl-CoA in pheromone glands (PGs), which in turn led to an increase in sex pheromone titer, female ability to attract males and successfully mating frequency in sugar-fed females. Consistently, sugar-fed females laid more eggs than water-fed females. Furthermore, the refeeding of starved females also caused significantly increase in the concentrations of trehalose, pyruvic acid, and acyl-CoA in PGs, thus facilitating a significant increase in sex pheromone production. Most importantly, RNAi-mediated knockdown of trehalase (leading to PG starvation) resulted in an increase in trehalose content, and decrease in the concentrations of pyruvic acid, and acyl-CoA in PGs, which in turn led to a decrease of sex pheromone titer, female ability to attract males and successful mating efficacy. Altogether, results revealed a mechanism by which sugar feeding contributed to trehalose utilization in PGs, promoted to significantly increased sex pheromone precursor by increasing the concentrations of pyruvic acid and acyl-CoA, and facilitated to sex pheromone biosynthesis and successful mating.

Pyruvate Kinase Is Required for Sex Pheromone Biosynthesis in Helicoverpa armigera

“…In the present study, we also found that sugar feeding increased the mRNA expression of PYK transcript and PYK activity, consistent with previous results (Krones et al, 2001;Kaloyianni et al, 2004), which indicated the conserved activation of PYK. These results were also consistent with the finding that the supplemental nutrition of female moth promoted the increase of trehalose, pyruvic acid, and acetyl-CoA levels in PGs, and the increase of sex pheromone production in H. armigera, M. separata, and H. virescens (Foster, 2009;Zhang et al, 2020), which elucidated the importance of the role of PYK in sex pheromone biosynthesis. Our results also demonstrated that PBAN treatment did not influence the mRNA level expression of the HaPYK transcript.…”

“…These results were in agreement with finding obtained for H. virescens, where the absence of sugar feeding decreased hemolymph trehalose concentration and the levels of acetyl-CoA, which finally decreased sex pheromone production (Foster, 2009). Similar results were also found in female M. separata, in which blocking of the sugar intake led to a decrease of glycolysis efficiency, as shown by the decrease in the concentrations of trehalose, pyruvic acid, and acetyl-CoA in the PGs, which finally resulting in the significant decrease of sex pheromone titer and subsequent mating efficiency (Zhang et al, 2020). These results were also consistent with the process of sex pheromone biosynthesis.…”

“…Thus, any factor that affects glycolysis will inevitably influence acetyl-CoA and sex pheromone production. This is the reason why changes in some of the factors, including adult supplemental nutrition, PYK, and trehalase finally affected sex pheromone biosynthesis in the present study and in a previous study (Foster, 2009 ; Zhang et al, 2020 ). In fact, many moths such as H. armigera, M. separata , and H. virescens have a habit of feeding on nectar, and usually synthesize sex pheromone by utilizing supplementary carbohydrate.…”

“…For instance, in female H. virescens , sugar feeding increases hamolymph trehalose concentration, which probably influences glycolysis in gland cells, thereby affecting the levels of acetyl-CoA and ultimately mediating sex pheromone production (Foster, 2009 ). Similarly, in female M. separata , sugar feeding facilitates the increase in the concentrations of trehalose, pyruvic acid, and acetyl-CoA in PGs, thereby resulting in the significant increase of sex pheromone titer, female ability to attract males, and successful mating frequency (Zhang et al, 2020 ). These results elucidated the importance of supplemental nutrition for sex pheromone biosynthesis in these moths.…”

“…Even most of the production of sex pheromone originates from a single feeding of moth (Foster and Anderson, 2015 ). Similarly, in Mythimna separata , sugar feeding markedly increases the concentrations of trehalose, which in turn increases pyruvic acid and acetyl-CoA production in PGs, thereby ultimately facilitating sex pheromone biosynthesis (Zhang et al, 2020 ). These results revealed that the importance of hemolymph trehalose to sex pheromone biosynthesis originated from supplementary nutrition.…”