Similarities between decapod and insect neuropeptidomes

Abstract

Background. Neuropeptides are important regulators of physiological processes and behavior. Although they tend to be generally well conserved, recent results using trancriptome sequencing on decapod crustaceans give the impression of significant differences between species, raising the question whether such differences are real or artefacts.Methods. The BLAST+ program was used to find short reads coding neuropeptides and neurohormons in publicly available short read archives. Such reads were then used to find similar reads in the same archives, and the DNA assembly program Trinity was employed to construct contigs encoding the neuropeptide precursors as completely as possible.Results. The seven decapod species analyzed in this fashion, the crabs Eriocheir sinensis, Carcinus maenas and Scylla paramamosain, the shrimp Litopenaeus vannamei, the lobster Homarus americanus, the fresh water prawn Macrobrachium rosenbergii and the crayfish Procambarus clarkii had remarkably similar neuropeptidomes. Although some neuropeptide precursors could not be assembled, in many cases individual reads pertaining to the missing precursors show unambiguously that these neuropeptides are present in these species. In other cases, the tissues that express those neuropeptides were not used in the construction of the cDNA libraries. One novel neuropeptide was identified: elongated PDH (pigment dispersing hormone), a variation on PDH that has a two-amino-acid insertion in its core sequence. Hyrg is another peptide that is ubiquitously present in decapods and is likely a novel neuropeptide precursor.Discussion. Many insect species have lost one or more neuropeptide genes, but apart from elongated PDH and hyrg all other decapod neuropeptides are present in at least some insect species, and allatotropin is the only insect neuropeptide missing from decapods. This strong similarity between insect and decapod neuropeptidomes makes it possible to predict the receptors for decapod neuropeptides that have been deorphanized in insects. This includes the androgenic insulin-like peptide that seems to be homologous to drosophila insulin-like peptide 8.

Transcriptomic characterization and curation of candidate neuropeptides regulating reproduction in the eyestalk ganglia of the Australian crayfish, Cherax quadricarinatus

“…In C. quadricarinatus we identified putative transcripts for ACP, corazonin and RPCH, but could not detect any GnRH or GnRH-like transcript in the de novo eyestalk transcriptome, perhaps because either (1) the eyestalk does not express these genes, (2) low expression level, or (3) the physiological stage at which the eyestalk RNA was isolated. This result coincides with a recent in silico mining investigation that included several decapods, where no trace of a GnRH/GnRH-like transcript could be found57. Interestingly, there is an evolutionary connection between GnRH, ACP, RPCH and corazonin at both the receptor and ligand level [(see a canonical review by Roch, et al 103…”

“…In crustaceans, a number of NP isoforms have been detected in M. rosenbergii 6, P. clarkii 7, S. paramamosain 5 and several decapod species57. From the current study, three NP isoforms were deduced; Cq -NP-1 and Cq -NP-2 have 12 cysteine residues (possibly forming 6 disulfide bridges), while Cq -NP-3 is a partial sequence with 16 cysteines.…”

“…Nevertheless, when comparing the current study with other recent comprehensive neuropeptidome studies in crustaceans57, a near-complete representation of the predicted neuropeptides are found, providing a solid foundation for future studies into the functionality of these neuropeptides in decapods.…”

“…In H. americanus , 35 precursors that released 194 distinct neuropeptides were detected from the neural tissues8. A very recent comprehensive collection of neuropeptides in a number of decapod species showcase a comprehensive list of characterised transcripts57 with high similarity between species, concluding that the gap between insects and crustaceans is narrow as far as the neuropeptide repertoire is concerned. A number of neuropeptides described in the above study by Veenstra were not detected in our dataset including Calcitonins, CFSH, CCRFamide, DILP7-like, Periviscerokinin and Trissin.…”

Gonadulins, the fourth type of Insulin-related peptides in Decapods

“…Neuropeptides and neurohormones originated early during evolution and are well conserved between crustaceans and insects (e.g. Veenstra, 2016). In several cases their functions are also the same or at least similar, this is e.g.…”