从转录组水平研究草鱼对饲料中赖氨酸的响应机制

Lysine is the first limited amnio acids of grass carp. Deficiency of lysine would cause growth reduction and high feed conversion ratio, In order to resolve lysine deficiency, it is necessary to supply crystalline amino acids in the practical diets, but there is controversy about the effective utilization of crystalline amino acids for fish. We had demonstrated that grass carp can effectively utilize Lyisne-HCL, which indicated good growth performance，and the body lipid content of grass carp was also significantly reduced with supplementation of crystalline lysine. But the molecular mechanism of lysine effect on grass carp metabolism was unclear. Transcriptome was a major linked factor between genome and proteome. Transcription manipulation was the most important manipulation way of life. In this study, we will integrate RNA-Sequencing and traditional nutrition research experiment to illuminate lysine effect on amino acids，fatty acids，energy metabolism pathway of grass carp with bioinformatics from transcriptome, we also want to find the relative target gene of lysine metabolism. Unigene related to lysine metabolism of grass cap will be founded and annotated.

赖氨酸是草鱼饲料中的第一限制性氨基酸，赖氨酸缺乏会导致草鱼生长受阻、饵料系数提高，同时使氮排放量增加，解决方法之一就是直接在饲料中添加晶体赖氨酸，但鱼类对晶体氨基酸的利用一直存在争议。我们前期实验表明草鱼能有效利用外源晶体赖氨酸，能显著促进草鱼生长且降低鱼体脂肪含量，但赖氨酸对草鱼代谢调控的分子机制并不清晰。转录组是连接基因组遗传信息与生物功能的蛋白质组的必然纽带，转录水平的调控是生物体最重要的调控方式之一。因此本项目将RNA-Sequencing技术和传统营养学实验相结合，利用生物信息学的方法从转录组水平阐明饲料中赖氨酸对草鱼氨基酸、脂肪酸、能量等代谢通路的影响，同时找到与赖氨酸代谢相关的Unigene基因，并首次完成草鱼转录组的基因注释，为鱼类分子营养学提供基础数据，并为晶体赖氨酸在水产饲料中应用提供新的思路。

为调查饲料脂肪和赖氨酸水平对草鱼生长影响，项目组设计了脂肪含量为5.4%和2.4%、赖氨酸含量为1.5%、1.7%和2%的6种饲料，将均重为3.00±0.02 g的健康草鱼随机分为6组，每组3个平行，每个平行30尾鱼开展为期8周的养殖实验。实验结果表明饲料低脂肪和高赖氨酸水平显著促进草鱼生长和饲料利用效率，饲料低脂肪水平显著降低草鱼体脂含量，同时发现饲料中脂肪和赖氨酸水平对草鱼生长和全鱼粗脂肪存在交互作用。 对低脂肪组不同赖氨酸水平的草鱼肝脏RNA-seq高通量测序发现，赖氨酸缺乏会导致PI3K-Akt signaling pathway, Rap1 signaling pathway, AMPK signaling pathway, Neuroactive ligand-receptor interaction, Cell adhesion molecules CAMs, Insulin signaling pathway, Adipocytokine signaling pathway等信号通路改变。实验结果有助于理解饲料赖氨酸对草鱼生理代谢改变的分子机制。