Identification of A-type allatostatins possessing -YXFGI/Vamide carboxy-termini from the nervous system of the copepod crustacean Calanus finmarchicus.
Allatostatins are important regulatory neuropeptides that inhibit juvenile hormone (JH) biosynthesis by the corpora allata (CA) in insects. However, to date, the structure and expression of the gene encoding allatostatins have not been reported in any species other than insects. In this study, we used a combination of a semi-nested polymerase chain reaction (PCR) and screening of a central nervous system cDNA library of Macrobrachium rosenbergii to isolate and sequence a cDNA clone (2885 bp) encoding a 701 amino acid FGLamide allatostatin precursor polypeptide. This is the first reported allatostatin gene in crustacean. The deduced precursor was conceptually split into at least 35 FGLamide allatostatins at dibasic cleavage sites (Lys and Lys/Arg), far more than reported for any other known FGLamide allatostatin precursors from insects (13-14 allatostatins). Reverse transcription-polymerase chain reaction (RT-PCR) analysis demonstrated that the gene was expressed in the brain, gut, thoracic and abdominal ganglia, but not in the heart, muscle, ovary, gill, or hepatopancreas. Furthermore, developmentally-dependent expression of the gene was observed in the brain and thoracic ganglia of the prawn by using semi-quantitative RT-PCR analysis.