Insight into the Regulatory Relationships between the Insulin-Like Androgenic Gland Hormone Gene and the Insulin-Like Androgenic Gland Hormone-binding Protein Gene in Giant Freshwater Prawns (Macrobrachium rosenbergii)

Giant freshwater prawns (Macrobrachium rosenbergii) are commonly found throughout the world. The size of the male giant freshwater prawn is much larger than that of the female. Therefore, understanding the molecular mechanism that underlies the sexual differentiation of M. rosenbergii is of both commercial and scientific importance. Insulin-like androgenic gland hormone (IAG) plays a key role in the differentiation of sex in M. rosenbergii. Although IAG has been investigated, the regulatory relationship between IAG and its binding protein partner, the insulin-like androgenic gland hormone-binding protein (IAGBP), has not been studied in M. rosenbergii. Here, we cloned and characterized the IAGBP from M. rosenbergii (Mr-IAGBP) for the very first time. Transcriptomic analysis showed that Mr-IAGBP mRNA was detected in a wide array of tissues with the highest expression found in the androgenic gland. The importance of IAG in male development was further demonstrated by an increase in IAG transcripts during the development of the androgenic gland and Mr-IAG was only highly transcribed in the androgenic gland of M. rosenbergii. Interestingly, we found that the Mr-IAG gene expression started during the 20th-day larva after hatching stage (LH20), followed (20th-day post-larval stage, PL20) by a gradual elevation of Mr-IAGBP levels. The levels of both genes peaked at the adult stage. The relationship between Mr-IAGBP and Mr-IAG was further analyzed using RNA interference. The injection of Mr-IAGBP double-stranded RNA (dsRNA) significantly reduced the transcription of Mr-IAG, while the amount of Mr-IAGBP mRNA and the translation of IAGBP protein was significantly reduced by the injection of Mr-IAG dsRNA. These results revealed that IAGBP is involved in IAG signaling. Furthermore, our data supports the hypothesis that (IAG and IAGBP)-IAG receptor signaling schemes exist in M. rosenbergii. Our results will provide important information for the further study of determining the sex of M. rosenbergii.