Table_6_Effect of Dietary Tryptophan on Growth, Intestinal Microbiota, and Intestinal Gene Expression in an Improved Triploid Crucian Carp.docx

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（Trp）在维持肠道功能方面受到了越来越多的关注。在本研究中，相较于对照组，喂食含6.35克/千克色氨酸的改良三倍体鲤鱼（ITCC）的饲料，ITCC的平均日增重（ADG）更高，肠道绒毛高度（VH）和隐窝深度（CD）也得到了改善。为了阐明潜在机制，我们利用RNA测序（RNA-seq）研究了肠道转录组的变化，并使用16S rRNA基因测序测量了ITCC在喂食6.35克/千克色氨酸后的肠道微生物群。膳食中的色氨酸改变了涉及营养运输和代谢的肠道基因表达。差异表达转录本（DETs）在包含蛋白质消化和吸收以及AMPK信号通路的关键途径中高度富集。16S rRNA测序显示，喂食6.35克/千克色氨酸显著增加了Cetobacterium属的丰度，以及门水平的厚壁菌门/拟杆菌门比例（P < 0.05）。此外，细菌丰富度指数（辛普森指数）在喂食6.35克/千克色氨酸的响应下显著增加（P < 0.05），提高了群落均匀度。综上所述，适量的膳食色氨酸可改善生长性能，并影响ITCC的肠道菌群。本研究可能有助于指导ITCC育种中膳食外源色氨酸的供应。