Abstract
The insulin-like androgenic gland hormone (IAG) is mainly produced in the androgenic gland (AG) of the male crustaceans and is a crucial regulator in male sexual differentiation. In the current study, the full-length cDNA of IAG in the swimming crab, Portunus trituberculatus (Pt-IAG), was cloned and characterized. Similar to other reported IAGs, the deduced amino acid sequence of Pt-IAG consists of signal peptide, B chain, C peptide, and A chain, containing six conserved cysteines that form two interchain disulfide bonds and one intra-B chain disulfide bond. Tissue distribution analysis suggested that the Pt-IAG cDNA was highly expressed in the AG and was slightly expressed in several other tissues. A short-term silencing of PtIAG with double-stranded RNA was found to reduce the transcript levels of insulin receptor (Pt-IR) and insulin-like growth factor-binding protein (Pt-IGFBP), suggesting the Pt-IAG might perform its biological function through the insulin family-based signaling system. Bilateral eyestalk ablation (ESA) induced the expression of Pt-IAG in the AG at 4 and 7 days after surgery, while the transcript levels of Pt-IR in the AG and testis and Pt-IGFBP in the muscle, testis, and thoracalia ganglia were significantly decreased from 1 day after surgery. The results suggested that the Pt-IR and Pt-IGFBP might also be the targets of eyestalk neuropeptides and responded to the ESA independent of IAG regulation.
Highlights
The insulin-like androgenic gland hormone (IAG) is an insulin-like hormone mainly produced in the androgenic gland (AG) of male crustaceans
The present study reported the first cloning of the IAG gene in P. trituberculatus (Pt-IAG), in parallel to the determination of its mRNA levels in different tissues and developmental stages
The presented study reported the first study of the IAG gene in the swimming crab, P. trituberculatus (Pt-IAG). quantitative real-time PCR (qPCR) analysis showed a predominant expression of Pt-IAG in the AG, which is consistent with all the previous studies
Summary
The insulin-like androgenic gland hormone (IAG) is an insulin-like hormone mainly produced in the androgenic gland (AG) of male crustaceans. Besides its role in sexual development, IAG was proposed to participate in the process of growth [3], glucose metabolism [4], and ovarian development [5]. Some early studies had noticed that eyestalk ablation (ESA) can lead to the hypertrophy and hyperactivity of AG, and it was eventually proposed that IAG production may be negatively regulated by the inhibitory neurohormone in the sinus gland of eyestalk through an eyestalk–AG endocrine axis [6]. The hypothesis was further supported by several studies showing an inhibitory role of specific eyestalk neuropeptides on IAG expression, such as gonad-inhibiting hormone (GIH) and molt-inhibiting hormone (MIH) in Macrobrachium nipponense [7] and crustacean female sex hormone (CFSH) in Scylla paramamosain [8]
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