Cloning, tissue expression, and nutritional regulation of the α-amylase gene in the herbivorous marine teleost Siganus canaliculatus

• The is the first report of α-amylase gene from a herbivorous marine-culture teleost.
• The cloning and characterization of α-amylase gene were identified from rabbitfish Siganus canaliculatus.
• The α-amylase transcript was primarily detected in hepatopancreas, anterior intestine, mid intestine and posterior intestine.
• The nutritional regulation of α-amylase synthesis in rabbitfish may occur at the posttranscriptional level.

Alpha-amylase (α-amylase) is a carbohydrase that plays a major role in carbohydrate metabolism. However, little is known about its molecular and biochemical characterisation in herbivorous marine teleosts. In the present study, an α-amylase gene was cloned and its tissue expression was determined in rabbitfish Siganus canaliculatus, a crucial cultured herbivorous marine teleost in China. The nutritional regulation of the gene, including its mRNA expression and enzymatic activity, was also investigated. The full length of its cDNA was 1903 bp, containing a 1539 bp open reading frame encoding a polypeptide of 512 amino acids, which possessed all the characteristic features of the α-amylase family. Its mRNA expression was detected in hepatopancreas, anterior intestine, middle intestine and posterior intestine, but not in other parts of the alimentary system. Four dietary groups of rabbitfish were each fed one of the following: raw fish (RF), formulated diet (FD), seaweed Enteromorpha prolifra (EP), or seaweed Gracilaria lemaneiformis (GL). After 8 weeks of feeding, the expression level of α-amylase mRNA in hepatopancreas, anterior intestine, middle intestine and posterior intestine showed no significant differences among the four dietary groups, whereas the α-amylase activity in the RF group was significantly lower than that in the other dietary groups (P < 0.001), and significantly higher in the mid and posterior intestine of fish fed GL than those in fish fed with EP (P < 0.01). These findings suggest that the nutritional regulation of α-amylase synthesis in rabbitfish may occur at the posttranscriptional level. This study is the first characterisation of the α-amylase gene from a herbivorous marine culture teleost.Statement of relevanceAlpha-amylase (α-amylase) is an important carbohydrase that plays a major role in carbohydrate metabolism. This study provides the first investigation of cloning and characterisation of α-amylase gene from a herbivorous marine-cultured teleost rabbitfish, and provides a foundation for the development of low-cost and effective formulated feed with seaweed as a dietary ingredient for rabbitfish. The work described has not been published or is under consideration for publication elsewhere. The study was reviewed and approved by the Ethics Committee of Animal Experiments of Shantou University.