Effects of Dietary Soybean Stachyose and Phytic Acid on Gene Expressions of Serine Proteases in Japanese Flounder（Paralichthys olivaceus）

Soybean stachyose （SBS） and phytic acid （PA） are anti-nutritional factors （ANF） which have deleterious effects on the growth and digestibility in fish. The present research studied the effects of dietary SBS and PA on the expression of three serine protease genes in the liver of Japanese flounder （Paralichthys olivaceus）. These genes are trypsinogen 1 （poTRY）, elastase 1 （poEL） and chymotrypsinogen 1 （poCTRY）. Eight artificial diets with graded levels of supplemented ANFs were formulated to 4 levels of SBS （0.00, 0.40, 0.80 and 1.50%）, 4 levels of PA （0.00, 0.20, 0.40 and 0.80）, respectively.Japanese flounder （initial weight 2.45 g ± 0.01 g） were fed with these diets for 10 weeks with three replications per treatment. At the end of 10 weeks, supplementation of 0.40% of dietary SBS or PA significantly increased the gene expression of poTRY and poCTRY （P0.05）. The same level of dietary SBS significantly decreased the gene expression of poEL. In comparison with the control group （ANF-free）,dietary PA （0.2% and 0.8%） significantly decreased the gene expression of poTRY, poCTRY and poEL （P0.05）. However, excessive supplement of dietary SBS （1.5%） has no significant effects on these gene expressions （P0.05）. These results suggested that dietary SBS and dietary PA could directly affect the serine protease genes at the transcriptional level in Japanese flounder, and these genes’expression was more sensitive to dietary PA than to SBS under the current experimental conditions.