Hormonal regulation of metamorphosis and reproduction in ticks

Abstract

The presence of a "status quo" hormone like JH has not been found in ticks. The most advanced understanding of tick endocrinology is associated with female reproduction, where the sequence of the first messages for storage proteins (vitellogenin (Vg) and carrier protein), the Vg receptor, and male peptidic pheromones were recently reported. The current consensus model suggests that ecdysteroids from the epidermis regulated by a putative peptidic ecdysiotrophic hormone from the synganlion initiates the expression of the Vg messages in fat body and midgut. Vg protein, secreted into the hemolymph, requires an ovary Vg receptor to be absorbed by oocytes. Male pheromones transferred into the female genital tract during mating initiate blood feeding to repletion and vitellogenesis. The work so far on tick endocrinology is limited by the paucity of identified hormones and the small number of studies on a few tick models. The role of storage proteins in the evolution of hematophagy is discussed.

In silico cloning of genes encoding neuropeptides, neurohormones and their putative G-protein coupled receptors in a spider mite

“…S1). There is no evidence for juvenile hormone in ticks (Neese et al, 2000;Roe et al, 2008), which makes its existence in mites dubious at best. However, both allatotropin and allatostatins have other physiological effects in insects (e.g.…”

“…Collections of neuropeptide GPCRs have been previously published for Drosophila melanogaster (Hewes and Taghert, 2001;Hauser et al, 2006a), Apis mellifera (Hauser et al, 2006b), Tribolium castaneum and Bombyx mori (Yamanaka et al, 2008;Shi et al, 2011). The sequences presented in these papers were included with the GPCR sequences obtained from the spider mite genome to construct phylogenetic trees.…”

“…6). Its receptor is likely encoded by tetur23g00700, a GPCR which has strong similarity (best BLAST e-value 6e-110) to the various insect allatotropin receptors recently characterized (Yamanaka et al, 2008;Vuerinckx et al, 2011;Horodyski et al, 2011;Nouzova et al, 2012) and which clusters tightly with those receptors on the phylogenetic tree (Fig. S1).…”

“…In those species the gene organization also suggests the production of two different mRNA's which each produce two different sets of peptides. (Hauser et al, 2006bYamanaka et al, 2008). GPCRs that have been deorphanized are followed by their ligand in the figure. A few other GPRs are indicated by the genus name of the species and the their gen bank accession number; in the latter cases sequences were sometimes corrected.…”

Ancestral reconstruction of tick lineages

“…Chitinases are regulated by ecdysteriods, which is a conserved feature among Ecdysozoa. Ecdysteriods (20-hydroxyecdysone) is synthesized in the epidermis of argasids and ixodids from dietary precursors (Kaufman, 2014;Roe et al 2014). In contrast to insects, juvenile hormone (JH) does not seem to be present or required by ticks for ecdysis, perhaps because ticks do not undergo metamorphosis .…”