Genome and transcriptome mining of the corazonin (Crz)-like peptide and gonadotropin-releasing hormone (GnRH)-like peptides in the spotted Babylon, Babylonia areolata

Abstract

The Spotted Babylon (Babylonia areolata) is an economically marine species in Thailand and other Asian countries. Due to the high demand for its meat, improving aquaculture practices for this species is essential. Regarding the lack of neuroendocrine control of reproduction in this species, we performed transcriptome analysis of the central nervous system and ovaries, and we searched against the reported genome of this animal species to find out the neurohormones. Here, we reported the identification of corazonin (ba-Crz)-like and gonadotropin-releasing hormone (ba-GnRH)-like mRNAs in B. areolata. The ba-Crz-like mRNA encoded mature ba-Crz-like peptide as QNYHYSNGWHP. Two ba-GnRH-like mRNAs encoded ba-GnRH-I-, and ba-GnRH-II-like peptides containing active peptides as QIHFSPTWGT and QIHFSHSWGT. Two introns were found in the ba-Crz-like gene while one intron was present in each ba-GnRH-like gene. These three peptides were phylogenetically placed in the molluscan Crz and GnRH clades. RT-PCR of these three mRNAs revealed their ubiquitous expressions across various organs, with all three predominantly expressed in ganglia, which was further confirmed by in situ hybridization of the cerebral ganglia. Immunohistochemistry showed positive signals for the Crz-like peptide in both the CNS and ovaries. To examine expression across ovarian cycle, the ba-Crz-like, and ba-GnRH-I-like mRNAs were consistently expressed in the CNS and ovaries of both immature and mature female snails, while the ba-GnRH-II-like mRNA significantly reduced its expression in the CNS of mature snails. Conclusively, this study was preliminary to report on the existence of GnRH/AKH/Crz peptides in the B. areolata, Further characterization of their receptors and biological functions is ongoing to ensure the GnRH, AKH, and Crz identification in this species.