Juvenile hormone in spiders. Is this the solution to a mystery?

EcR/USP-1-mediated ecdysteroid signaling regulates wolf spider (Pardosa pseudoannulata) development and reproduction

Lycosidae females demonstrate meticulous maternal care of offspring by carrying egg sacs and juvenile spiderlings during the reproductive stage. Nuclear receptors (NRs), especially the ecdysone receptor (EcR) and ultraspiracle (USP), have attracted considerable attention in the regulation of arthropod development and reproduction due to their pivotal roles in ecdysteroid signaling cascades. In the present study, 23 NRs, including one EcR and two USPs, were identified in the genome of the predatory wolf spider Pardosa pseudoannulata. RNA interference (RNAi) targeting EcR and USP-1 inhibited spiderling development and resulted in non-viable eggs in the egg sacs. EcR and USP-1 responded to changes in ecdysteroid levels, and interference in ecdysteroid biosynthesis led to similar phenotypes as dsEcR and dsUSP-1 treatments. These findings suggest that EcR/USP-1-mediated ecdysteroid signaling regulates P. pseudoannulata development and reproduction. The P. pseudoannulata females with suppressed ecdysteroid signaling proactively consumed their non-viable egg sacs, resulting in a 7.19 d shorter first reproductive cycle than the controls. Termination of the failed reproductive cycle enabled the spiders to produce a new egg sac more rapidly. This reproductive strategy may partially rescue the reduction in population growth due to non-viable eggs and compensate for the physiological expenditure of wasted maternal care, which would be beneficial for the conservation of P. pseudoannulata populations and their natural control of insect pests.

Regulation of juvenile hormone and ecdysteroid analogues on the development of the predatory spider, Pardosa pseudoannulata, and its regulatory mechanisms

Insecticides harm the beneficial organisms, such as predatory spiders, through direct killing or regulation of the development and reproduction. In this study, the bioassay showed that the treatment of juvenile hormone (JH) analogue fenoxycarb delayed the moulting of Pardosa pseudoannulata, a dominant predatory spider in paddy fields. In order to figure out the regulatory mechanism of fenoxycarb on the spider development, we systematically analyzed JH biosynthesis in P. pseudoannulata. All genes involved in JH biosynthesis pathway were retrieved from the genome of P. pseudoannulata, except for CYP15A1. The absence of CYP15A1 was in agreement with the identification of methyl farnesoate (MF) rather than JH III in the spider. The delayed moulting and decreased expression of JH biosynthesis-related genes in the MF-applied spiderlings supported that MF was an active JH. Fenoxycarb treatment significantly upregulated the transcriptional level of JH biosynthesis-related genes and consequently delayed the spiderling moulting. In the spider development, ecdysteroid played the opposite role, in contrast to MF, to accelerate the development, as our previous study. Here we found that the treatment of ecdysteroid analogue tebufenozide accelerated P. pseudoannulata spiderling moulting, which resulted from the expressional suppression of ecdysteroid biosynthesis-related genes. In total, the JH and ecdysteroid analogues affected the development of P. pseudoannulata by the expressional regulation of biosynthesis-related genes, which would be helpful for the evaluation of hormone analogue insecticides in environmental safety, and useful for the protection and application of P. pseudoannulate and related spider species.

Molecular Characterization of the Cytochrome P450 Epoxidase (CYP15) in the Swimming Crab Portunus trituberculatus and Its Putative Roles in Methyl Farnesoate Metabolism

CYP15, which encodes a microsomal cytochrome P450 enzyme, could be involved in juvenile hormone biosynthesis in insects. In this study, a full-length cDNA of CYP15 was cloned from the swimming crab Portunus trituberculatus. This PtCYP15 amino acid sequence contains six conserved domains, which is a typical feature of the cytochrome P450 family. Phylogenetic tree analysis results showed that PtCYP15 clusters in a single branch of crustacean species, suggesting that CYP15 may be more widely present in crustaceans. The PtCYP15 mRNA has a broad pattern of tissue expression in P. trituberculatus, including high levels of expression in the hepatopancreas of both sexes and in the ovary of female crabs. During ovarian development stages, PtCYP15 mRNA is highly expressed in stages I and II and less so in stages III and IV in the hepatopancreas and the ovary of the female crabs. These expression profiles are opposite those of methyl farnesoate in hemolymph, suggesting that PtCYP15 might be involved in methyl farnesoate metabolism. In vitro studies show that only methyl farnesoate upregulated vitellogenin expression in the hepatopancreas, suggesting that methyl farnesoate might be the equivalent of juvenile hormone III in crustaceans. Methyl farnesoate treatment increased levels of PtCYP15 in explants of the hepatopancreas and ovary, while juvenile hormone III treatment reduced levels of PtCYP15 mRNA in ovary explants, suggesting that PtCYP15 might be involved in degrading methyl farnesoate. Furthermore, PtCYP15 mRNA expression levels were inhibited by adding juvenile hormone III to ovary explants. These findings provide foundational information for future research on methyl farnesoate metabolism in crustaceans.