PhD Exit Seminar – Laura Sedra (Lange lab)

PhD Exit Seminar

Friday June 3^rd, 1:30 pm – Room IB 250, University of Toronto at Mississauga

Laura Sedra (Lange lab)

“FMRFamide-like peptides and their role in reproduction in the Chagas vector, Rhodnius prolixus“

Abstract

Insect reproductive systems are tightly modulated by neurotransmitters via direct innervation, by neurohormones circulating in the haemolymph and by neuromodulators locally released from endocrine cells in the periphery. FMRFamide-like peptides (FLPs) are large families of neuropeptides with conserved RFamide C-termini and have been implicated in vertebrate and invertebrate neuroendocrinology. This thesis examines the differing roles that members of the FLP superfamily have in the adult female reproductive system of Rhodnius prolixus. The entire female reproductive tract is composed of different arrangements of striated muscles. Two members of the N-terminally extended FM/L/IRFamides have been shown to stimulate ovariole, ovary, oviduct and bursal muscle contraction in a dose-dependent manner; whereas the myosuppressin, RhoprMS, does not have any myogenic effect on the reproductive tract. The RhoprNPF (neuropeptide F) and RhoprNPF receptor (RhoprNPFR) genes have been cloned from the R. prolixus central nervous system (CNS) and phylogenetic analysis implies possible receptor-ligand co-evolution. RhoprNPFR has been classified as a G-protein coupled receptor (GPCR) containing 7 transmembrane domains and a conserved 8th α-helix that is a classic characteristic of rhodopsin-type GPCRs. FMRFamide-like immunoreactivity (FLI) was observed in cells and processes in the adult CNS and processes on the reproductive tract; moreover a specific subset of median neurosecretory cells (MNSCs) in the brain, as well as small cell bodies along the muscle fibers of the lateral oviduct, express the RhoprNPF transcript. The RhoprNPFR transcript is also expressed in putative nurse cells in the germarium and pre-follicular cells of the R. prolixus telotrophic ovariole. RhoprNPFR transcript appears to be supplied to the developing oocyte during vitellogenesis and the receptor most likely aids in the differentiation of pre-follicular cells into mature follicle cells surrounding the growing oocyte and helps regulate the supply of nutrients. Screening members of the FLP family in an egg-laying assay showed that N-terminally extended FM/L/IRFamides and short NPF stimulate oogenesis, whereas MS inhibits it. Although RhoprNPF does not have a myogenic effect on lateral oviduct muscle, we have shown that it potentially aids in ovulation. Sulfakinins exhibit no effect on egg-laying. In summary, this thesis demonstrates the importance of FLPs in the control and regulation of the female R. prolixus reproductive system.