Carnosine concentration and expression profiles of carnosine related genes in Mytilus after beta-alanine injection

Carnosine and its analogues are histidine-containing dipeptides(HCDs)playing diverse functions in vertebrates.However,the distribution and the metabolism of carnosine in invertebrates are still unknown.In this study,Mytilus coruscus,a shellfish with important economic value in China,was selected for the investigation of HCD content and the expression profiling of carnosine-related genes in various mussel tissues.Quantification of HCD by amino acids analyzer revealed a low concentration of anserine in muscular tissues in Mytilus,indicating the presence of HCD even in an invertebrate.mRNA expression of five carnosine metabolic-related genes was profiled in various tissues,and the results highlighted the relative higher expression level of these genes in muscular tissues.Considering the fact that beta-alanine supplementation can increase the HCD content in vertebrates,a beta-alanine injection was performed and the changes of HCD concentration and the mRNA expression of carnosine related genes were investigated in five mussel tissues.The results revealed the increase of HCD concentration,as well as the up-regulated expression level of related genes,in tested tissues of beta-alanine injected mussels.Transcriptomic analysis for the whole soft tissue of mussel before and after beta-alanine injection were performed,and 3569 differential expression genes(DEGs)were identified in the beta-alanine injected group when compared to their expression levels in the control.These data indicated the complex eff ects of betaalanine on M.coruscus metabolism,and those DEGs enriched in pathways of cancers,muscle contraction,and tyrosine metabolism highlighted the possible functions of beta-alanine in cell proliferation,sports,and melanogenesis,respectively.