Journal of Aquaculture Research & Development

Abstract

Transcriptome Analysis Reveals L-amino Acids as Olfactory Stimulant in the Large Yellow Croaker (Larimichthys crocea)

Awonfor Franklyn, Yajun Wang, Na Yu, Jianbo Wang, Qijun Le, Xiaohuan Cao and Huakun Zheng

Similar to bony fish, feeding preference in Larimichythys crocea is determined by the smell and taste of food which is mainly controlled by the olfactory system. Ten different L-types of amino acids at different concentration levels were introduced to the large yellow croaker and significant differences in the olfactory response with reference to odor detection were observed. Movement and feeding responds were taken within a 4-minutes interval which showed an increase in the responsiveness of the fish with increase in the concentration of specific amino acid from 0.01 M/L to 0.08 M/L. There was a significant difference between different kinds of amino acid with high responses from L-Arginine and L- Tryptophan. The olfactory epithelium before and after administering L-amino acid was observed and it showed remarkable differences with the top of the cilia being inflated in the administered amino acid samples. RNA sequenced was done with Illumina HiSeq 2500 in which 40326272 and 35794904 clean reads from two amino acids namely L- Arginine and L-Tryptophan were acquired respectively and more than 845% of the read were mapped to the reference genome. Comparing the gene expression of two L-types amino acid, 16701 unigenes were significantly differentially expressed including 10142 up-regulated and 6503 down-regulated genes. 100 olfactory receptor genes were detected, these genes include; Olfactory receptors (OR), Vomeronasal receptors (VR) and Trace-Amine Associated Receptors (TAAR) with low levels of Olfactomedin like Protien (OLFM) genes. OR expressed genes were then selected for further quantitative RT-PCR analysis. With the use of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of the differential expressed genes were found out that multiple genes were involve in olfactory activities such as signaling, single organism signaling, cell communication and olfactory transduction. These transcriptome analyses provide clear information on olfactory related genes expression of Larimichthys crocea with respect to L-type amino acids. Also, this study help us identify which L-type amino acid is a potent phagostimulant to the fish and how it can be employed in the fish feed thereby increasing the protein intake of the fish.