An amine oxidase gene from mud crab, Scylla paramamosain, regulates the neurotransmitters serotonin and dopamine in vitro.

Junguo Liu,Wei Song,Lingbo Ma,Xiu Li,Yan Pi,Fengying Zhang,Ming Zhao,Keji Jiang,Le Diao,Yi Hu

doi:10.1371/journal.pone.0204325

Abstract

Amine oxidase, which participates in the metabolic processing of biogenic amines, is widely found in organisms, including higher organisms and various microorganisms. In this study, the full-length cDNA of a novel amine oxidase gene was cloned from the mud crab, Scylla paramamosain, and termed SpAMO. The cDNA sequence was 2,599 bp in length, including an open reading frame of 1,521 bp encoding 506 amino acids. Two amino acid sequence motifs, a flavin adenine dinucleotide-binding domain and a flavin-containing amine oxidoreductase, were highly conserved in SpAMO. A quantitative real-time polymerase chain reaction analysis showed that the expression level of SpAMO after quercetin treatment was time- and concentration-dependent. The expression of SpAMO tended to decrease and then increase in the brain and haemolymph after treatment with 5 mg/kg/d quercetin; after treatment with 50 mg/kg/d quercetin, the expression of SpAMO declined rapidly and remained low in the brain and haemolymph. These results indicated that quercetin could inhibit the transcription of SpAMO, and the high dose (50 mg/kg/d) had a relatively significant inhibitory effect. SpAMO showed the highest catalytic activity on serotonin, followed by dopamine, β-phenylethylamine, and spermine, suggesting that the specific substrates of SpAMO are serotonin and dopamine. A bioinformatics analysis of SpAMO showed that it has molecular characteristics of spermine oxidase, but a quercetin test and enzyme activity study indicated that it also functions like monoamine oxidase. It is speculated that SpAMO might be a novel amine oxidase in S. paramamosain that has the functions of both spermine oxidase and monoamine oxidase.

Highlights

Mud crab, Scylla paramamosain are economically important crustaceans cultured in brackish coastal waters of the Southwest Pacific Ocean and North Indian Ocean [1]
The flavin-containing amine oxidoreductase domain is conserved among many amine oxidases, including maze polyamine oxidase (PAO) and various flavin-containing monoamine oxidase (MAO)
Based on the match information of the sequences, we observed that only residues F168 and Y398 of Homo sapiens MAO-B were coincident with SpAMO

Summary

Introduction

Scylla paramamosain are economically important crustaceans cultured in brackish coastal waters of the Southwest Pacific Ocean and North Indian Ocean [1]. The crabs’ aggressive behaviour is a bottleneck problem during crab culturing and has caused severe economic losses. Molt is crucial in development and reproduction of crustaceans. This can be deduced from two main aspects: crustaceans are highly vulnerable to cannibalism during the molting process because their new shell is incompletely calcified; the potential victim can become the attacker on smaller conspecifics after successful molting because substantial size increases [6,7]. The traditional breeding method can only reduce the cannibalize rate by increasing bait quantity, reducing the crab density and setting up shelters, among other measures. There are few studies on the crabs’ aggressive behaviour; we hope to discover the genes related to aggressive behaviour in S. paramamosain, and to explore the molecular foundation behind the aggressive behaviour

Methods

Results

Conclusion