Abstract
Pyruvate kinase (PYK) is a speed-limited enzyme of glycolysis that catalyzes the formation of pyruvate, and plays an important role in acetyl-CoA synthesis. The acetyl-CoA is the precursor of sex pheromone biosynthesis in Helicoverpa armigera. However, the role of PYK in sex pheromone biosynthesis remains elusive. Here, PYK in H. armigera (HaPYK) was found to be highly expressed in the pheromone glands (PGs). The developmental expression profile of HaPYK was consistent with the fluctuation of sex pheromone release. Function analysis revealed that the knockdown of HaPYK led to a decrease in the levels of pyruvic acid and acetyl-CoA in PGs, which in turn caused a significant decrease in cis-11-hexadecenal (Z11-16: Ald) production, female capability to attract males, and mating frequency. Further study demonstrated that sugar feeding (5% sugar) increased the transcription and enzyme activity of HaPYK, thereby facilitating sex pheromone biosynthesis. Moreover, pheromone biosynthesis activating neuropeptide (PBAN) upregulated HaPYK activity through protein kinase C (PKC), as shown by PKC-specific inhibitor analysis. Altogether, our results revealed that PBAN activated HaPYK by Ca2+/PKC, thereby regulating the synthesis of pyruvate and subsequent acetyl-CoA, ensuring the supply of sex pheromone precursor, and finally facilitating sex pheromone biosynthesis and mating behavior.
Highlights
Powerful reproduction capacity is an important reason why insects are the most prosperous species on earth
Results demonstrated that the injection of dsHaPYK in females led to a significant decrease in the expression of HaPYK transcript, compared with those in females injected with dsEGFP (Figure 2A)
The effects of HaPYK knockdown on sex pheromone production and subsequent mating behaviors were further investigated, and the results showed that RNAi-mediated knockdown of HaPYK significantly reduced the production of sex pheromone regulated by pheromone biosynthesis activating neuropeptide (PBAN), as shown by GS/MS analysis, compared with the controls that were injected with dsEGFP (Figure 3A)
Summary
Powerful reproduction capacity is an important reason why insects are the most prosperous species on earth. Insects have evolved various ways to communicate to ensure the normal mating and reproduction. Lepidopteran female moths usually use sex pheromone as chemical signal for long-distance communication. Sex pheromone compounds are divided into type I, type II, and miscellaneous (Ando et al, 2004). Type I sex pheromones are characterized by a C10–C18 straight chain with zero to three double bonds at various positions and with different configurations (Ando et al, 2004). Typical type I compounds have a functional group at the terminal position, such as alcohol, ester, or aldehyde functional groups (Wei et al, 2006). Typical type-I compounds are biosynthesized in insect species belonging to the families of Bombycidae, Noctuidae, Sesiidae, Tortricidae, and several others.
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