Table_7_Effect of Dietary Tryptophan on Growth, Intestinal Microbiota, and Intestinal Gene Expression in an Improved Triploid Crucian Carp.xlsx

Tryptophan (Trp) has received increasing attention in the maintenance of intestinal function. In this study, improved triploid crucian carp (ITCC) fed diets containing 6.35 g kg−1 Trp had higher average daily gain (ADG) and improved villus height (VH) and crypt depth (CD) in the intestine compared to the control group. To elucidate the potential mechanisms, we used RNA sequencing (RNA-seq) to investigate changes in the intestinal transcriptome and 16S rRNA gene sequencing to measure the intestinal microbiota in response to 6.35 g kg−1 Trp feeding in ITCC. Dietary Trp altered intestinal gene expression involved in nutrient transport and metabolism. Differentially expressed transcripts (DETs) were highly enriched in key pathways containing protein digestion and absorption and the AMPK signaling pathway. 16S rRNA sequencing showed that 6.35 g kg−1 Trp significantly increased the abundance of the genus Cetobacterium, and the Firmicutes/Bacteroidetes ratio at the phylum level (P < 0.05). In addition, bacterial richness indices (Simpson index) significantly increased (P < 0.05) community evenness in response to 6.35 g kg−1 Trp. In conclusion, appropriate dietary Trp improves the growth performance, and influences the intestinal flora of ITCC. This study might be helpful to guide the supply of dietary exogenous Trp in ITCC breeding.

色氨酸（Tryptophan, Trp）在维持肠道功能方面受到的关注日益增加。本研究中，饲喂含6.35 g·kg⁻¹色氨酸日粮的改良型三倍体鲫鱼（improved triploid crucian carp, ITCC），其平均日增重（average daily gain, ADG）显著高于对照组，且肠道绒毛高度（villus height, VH）与隐窝深度（crypt depth, CD）得到改善。为阐明潜在作用机制，本研究采用RNA测序（RNA-seq）探究ITCC肠道转录组的变化，并通过16S rRNA基因测序检测饲喂6.35 g·kg⁻¹色氨酸日粮后其肠道菌群的响应情况。日粮色氨酸可调控参与营养物质转运与代谢的肠道基因表达。差异表达转录本（differentially expressed transcripts, DETs）显著富集于蛋白质消化吸收、AMPK信号通路等关键通路。16S rRNA测序结果显示，6.35 g·kg⁻¹色氨酸可显著提高梭菌属（Cetobacterium）的丰度，以及门水平下的厚壁菌门/拟杆菌门比值（P < 0.05）。此外，日粮色氨酸还可显著提升菌群丰富度指标辛普森指数（Simpson index），并改善群落均匀度（P < 0.05）。综上，适宜水平的日粮色氨酸可提升改良型三倍体鲫鱼的生长性能，并调控其肠道菌群结构。本研究可为改良型三倍体鲫鱼养殖过程中外源日粮色氨酸的添加提供理论指导。