The Use of Mass Isotopomer Distribution Analysis to Quantify Synthetic Rates of Sex Pheromone in the Moth Heliothis virescens

Abstract

Although there has been much investigation of the steps involved in sex pheromone biosynthesis in moths, little is known about the kinetics of biosynthesis in vivo, primarily because there are few techniques suitable for studying the small amounts of pheromone produced without perturbing a female moth's normal physiology. In this paper, female Heliothis virescens moths fed on U-(13)C-glucose were subjected to mass isotopomer distribution analysis, enabling calculation of fractional (FSR) and absolute (ASR) synthetic rates of the main pheromone component, (Z)-11-hexadecenal, at two different photoperiodic times: during the scotophase (when adults are sexually active) and during the photophase (when adults do not engage in mating behavior). FSRs differed substantially at the two times with, as expected, the greater rate occurring during the scotophase. After determining Z11-16:Ald pool sizes, ASR through the scotophase was calculated to be roughly 20 times greater than ASR in the photophase. These differences are consistent with the release/non-release of the pheromone biosynthesis-activating neuropeptide. This approach should facilitate determination of more quantitative measures of semiochemical production in moths and other sugar-feeding insects that synthesize semiochemicals from glycolytic metabolites.

Sex pheromones in mate assessment: analysis of nutrient cost of sex pheromone production by females of the mothHeliothis virescens

“…This suggests that the proportions of carbohydrate and fat used for de novo pheromone biosynthesis are not fixed but change according to endogenous conditions of the female, although probably not greatly. Using [U- (Foster and Anderson, 2011). This lower FSR is possibly due to inhibitory effects of the bolus of acid in DMSO on biosynthetic enzymes (Foster, 2005a).…”

“…30% of the total labeled pheromone, over that predicted by mass isotopomer distribution analysis (MIDA). Given the rapid turnover of pheromone during the scotophase (Foster and Anderson, 2011), this EUP likely comes from stored precursor acids converted directly to pheromone. If so, then ca.…”

“…The relatively large amount of EUP 4 h after feeding in the photophase must be taken into account with the relatively low amounts of pheromone produced during this period. It could result from either a relatively high (compared with de novo biosynthesis) production of pheromone from stored precursor acids or a slow turnover during this period of previously synthesized (unlabeled) pheromone (Foster and Anderson, 2011), especially as 24 h later EUP was much lower.…”

“…Adult Lepidoptera commonly feed on carbohydrate in plant nectar, which typically increases female fecundity (Wäckers et al, 2007). In the polyandrous moth Heliothis virescens Fabricius (Lepdioptera, Noctuidae), this adult-acquired carbohydrate (AAC) is also used for pheromone biosynthesis via uptake to hemolymph (as trehalose), followed by glycolysis and pyruvate oxidation to cytosolic acetyl CoA (Foster and Anderson, 2011;Foster, 2009;Foster and Johnson, 2010). Although this demonstrates that pheromone can be made from carbohydrate, we do not know whether this is the sole nutrient used or the relative importance of adult-versus larval-acquired nutrients.…”

“…C]glucose as a tracer (Foster and Anderson, 2011). [16,16,16-D 3 ]-Hexadecenoic acid (D 3 -16:COOH) injected into females was rapidly converted to pheromone (Fig.…”