Mating activates the heme peroxidase HPX15 in the sperm storage organ to ensure fertility in Anopheles gambiae

Abstract

Anopheles gambiae mosquitoes are major African vectors of malaria, a disease that kills more than 600,000 people every year. Given the spread of insecticide resistance in natural mosquito populations, alternative vector control strategies aimed at reducing the reproductive success of mosquitoes are being promoted. Unlike many other insects, An. gambiae females mate a single time in their lives and must use sperm stored in the sperm storage organ, the spermatheca, to fertilize a lifetime's supply of eggs. Maintenance of sperm viability during storage is therefore crucial to the reproductive capacity of these mosquitoes. However, to date, no information is available on the factors and mechanisms ensuring sperm functionality in the spermatheca. Here we identify cellular components and molecular mechanisms used by An. gambiae females to maximize their fertility. Pathways of energy metabolism, cellular transport, and oxidative stress are strongly regulated by mating in the spermatheca. We identify the mating-induced heme peroxidase (HPX) 15 as an important factor in long-term fertility, and demonstrate that its function is required during multiple gonotrophic cycles. We find that HPX15 induction is regulated by sexually transferred 20-hydroxy-ecdysone (20E), a steroid hormone that is produced by the male accessory glands and transferred during copulation, and that expression of this peroxidase is mediated via the 20E nuclear receptor. To our knowledge, our findings provide the first evidence of the mechanisms regulating fertility in Anopheles, and identify HPX15 as a target for vector control.

Sexual transfer of the steroid hormone 20E induces the postmating switch in Anopheles gambiae

“…During mating males transfer large amounts of 20E, a strong regulator of gene expression (28), that is released gradually from the mating plug into the female reproductive tract over the first day after copulation (17). We observed that a considerable number of genes (vitellogenin, prophenoloxidases, proteasome subunits, V-type ATPases, cytochrome P450s, MISO, the heme peroxidase HPX15) identified in our microarrays analysis generally are regulated by 20E in Anopheles and other insects (17,25,(29)(30)(31)(32). Therefore we explored the full extent of a possible 20E-mediated regulation of postmating transcriptional activity by comparing the transcriptional profile of the female reproductive tract observed at 24 hpm and the transcriptional response induced in the atrium and spermatheca at the same time point after injection of r = 0.58 Log 2 -transformed fold-change data from unique array identifiers showing significant differences (P < 0.05 mating, P < 0.01 20E treatment) are correlated.…”

“…To gain better insight into the molecular link between the postmating transcriptional and morphological changes and the behavioral and physiological shift induced by copulation (3,17,25), we initially performed an indepth transcriptional analysis of the female lower reproductive tract (LRT), comprising the atrium and the spermatheca. To identify the molecular pathways specifically regulated in these female reproductive tissues, we analyzed three time points (3,12, and 24 h post mating; hpm) that would capture transcriptional changes occurring within a broad time window after copulation.…”

Stimulating Anopheles gambiae swarms in the laboratory: application for behavioural and fitness studies

“…Little information is available on the male–female-environment interactions during mating [3, 4, 7, 16] and little is known of the molecular mechanisms that regulate these processes [17, 18]. …”

Identification of an Anopheles Lineage-Specific Unique Heme Peroxidase HPX15: A Plausible Candidate for Arresting Malaria Parasite Development

“…Here this research group demonstrated that AgHPX15 induction in female spermathica is regulated by sexually transferred 20-hydroxyecdysone (20E), which is essential to preserve the functionality of stored sperm and long-term fertility [43]. Thus, targeting AgHPX15 will disrupt the reproductive cycle and numbers of mosquitoes in the field.…”