A novel function of bursicon in stimulation of vitellogenin expression in black tiger shrimp, Penaeus monodon

Abstract

© 2015 Elsevier B.V. Bursicon is a cystine knot glycoprotein hormone that is composed of two subunits; alpha and beta. Bursicon plays several physiological roles in insects and crustaceans such as cuticle tanning, wing expansion and molting process. Because of its structural similarity with vertebrate gonadotropins, this study therefore aimed to investigate a novel function of bursicon in vitellogenin (Vg) stimulation in reproductive female shrimp, Penaeus monodon. Full-length cDNAs encoding the alpha and beta subunits of bursicon in P. monodon (Pmbursα and Pmbursβ) were obtained by rapid-amplification of cDNA ends. Both Pmbursα and Pmbursβ mRNA levels were dominantly expressed in subesophageal ganglia and thoracic ganglia. The expression of Pmbursα and Pmbursβ in subesophageal ganglia was significantly increased in early-vitellogenic stage of ovarian development suggesting a possible role of bursicon in vitellogenesis. To study the function of bursicon in shrimp reproduction, recombinant Pmbursα (rbursα), Pmbursβ (rbursβ) and Pmbursαβ (rbursαβ) were successfully expressed in the methylotrophic yeast, Pichia pastoris. A treatment of shrimp ovarian cells with recombinant Pmburs showed that only rbursαβ could induce the expression of Vg mRNA. In addition, injection of rbursαβ into female P. monodon broodstock caused an increase of Vg mRNA expression in the ovary as well as stimulated ovarian development. This study provides the first evidence for a reproductive role, most likely as an invertebrate neuropeptide gonad-stimulating hormone, of the heterodimeric bursicon in P. monodon.