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-1inhibited spiderling development and resulted in nonviable eggs in the egg sacs. EcR and USP-1responded to changes in ecdysteroid levels, and interference in ecdysteroid biosynthesis led to similar phenotypes as ds EcR and ds USP-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.

Molecular characterization and functional analysis of USP-1 by RNA interference in the Asian gypsy moth Lymantria dispar

Ecdysteroids play an important role in regulating diverse physiological processes in arthropods,such as molting,metamorphosis,reproduction and diapause.Ecdysteroids mediate the response by binding to a heterodimeric complex of two nuclear receptors:the ecdysone receptor and the ultraspiracle(USP).To investigate the role of USP in development of the Asian gypsy moth(Lymantria dispar),a USP cDNA was obtained from the transcriptome of L.dispar and verified by PCR.In-depth profiling of transcript levels of L.dispar USP-1(LdUSP-1)at different developmental stages and over time in thirdinstar larvae and different tissues isolated during the thirdinstar stage of L.dispar was then carried out.Transcript levels of LdUSP-1 were relatively high before 72 h in the third-instar larvae after ecdysis and in the adult male.The function of LdUSP-1 in molting was analyzed by knockdown of LdUSP-1 in third instar larvae using RNA interference.Silencing of LdUSP-1 significantly downregulated the transcript level of E75,an ecdysone-inducible gene,and of Sad,a Halloween gene.In addition,the duration of the third-instar stage was slightly shortened and larval mortality increased after the LdUSP-1 knockdown.