人参驯化过程中群体水平的基因分化及表达变异研究

Domestication is a special model of evolution under the human beings’ choice. Under artificial selections, the genetic diversity and gene expression diversity of domesticated species have a rapid and significant effect on phenotype and physiological function, which improved the adaptability to artificial environment. Panax ginseng belongs to Araliaceae, having significantly medicinal and economic values. Cultivars of P. ginseng were domesticated from the wild populations. The cultivars’ morphological characteristics, especially the root phenotype had changed significantly. Since P. ginseng is a genetically complicated and large (3.2G) heterotetraploid, both genetic differentiation and expression variation are rarely revealed through the domestication process of P. ginseng. The primary goal of this project is to carry out full-length transcriptome sequencing and deep RNA sequencing of wild P. ginseng and cultivars, constructing reference transcript. After getting the SNP dataset based on RNA sequence differences, we’ll reveal the effects of domesticating on genetic structure, and domestication pattern of P. ginseng. Then we’ll compare the differences of gene expression between wild and cultivars populations, and speculate about the effect of domestication on gene expression, and reveal different cultivars’ adaptability to artificial domesticated environment. This project will be helpful to elaborate on the domestication pattern of cultivated P. ginseng, and also the molecular mechanism of P. ginseng domestication. Our study will lay the theoretical foundation for molecular breeding and improvement, and provide a scientific basis.

驯化是人类参与下物种演化的特殊模式。在人工选择下，驯化物种的遗传多样性和基因表达水平快速地产生显著变异；同时，驯化物种的表型和生理性状发生改变，以提高其对驯化环境的适应能力。人参隶属五加科人参属，具有重要的药用价值和经济价值。栽培人参由野生人参驯化而来，根部表型明显变异，已培育出多个品系。由于人参是基因组偏大（约3.2G）的异源四倍体，基因组较为复杂，故对其驯化过程中基因分化和表达变异的研究比较少。本项目拟对人参群体进行全长转录组测序和深度RNA测序，构建人参参考转录本；基于RNA序列差异获得SNP数据集，分析驯化过程对栽培人参遗传结构的影响，揭示人参的驯化模式；分析人参群体的差异表达基因，推断驯化对基因表达的影响，揭示不同品系的栽培人参对人工驯化环境的适应能力。本项目有助于揭示栽培人参的驯化模式，阐述人参驯化的分子机制，为分子育种和改良奠定理论基础、提供科学依据和参考。

栽培人参驯化于野生人参，但栽培人参在形态，生长年限和生理状态都与野生人参存在差异。本研究以野生人参和栽培人参为研究对象，主要围绕以下内容展开研究：（1）人参驯化过程中群体水平的基因分化及表达变异研究。（2）不同品系栽培人参间基因表达差异的研究。（3）不同品系栽培人参根际细菌和真菌群落差异的研究。（4）野生人参和栽培人参中根际微生物群落的差异研究。（5）生长年限对野生人参和栽培人参基因表达影响的研究。研究结果发现：人参可能是经历了多次独立驯化，且野生人参与栽培人参间存在基因渐渗。对不同品系栽培人参（即普通参，石柱参，边条参和高丽参）进行了转录组测序和多糖含量分析，发现四个品系栽培人参的根中多糖含量明显不同，共鉴定出参与人参多糖合成的19种酶。不同品系栽培人参间的微生物群落结构差异明显，Bacillus，Alternaria alternata和Cladosporium sp.agrAR069可能与不同人参品系的抗病性相关。野生人参的根际微生物群落与栽培人参根际微生物群落存在显著差异。栽培人参根际微生物中Chlorofexi, Fusarium 和 Alternaria的丰度显著高于野生人参。不同生长年限的栽培人参间差异表达基因(DEGs)的数量多于不同生长年限的野生人参间的DEGs。生长年限对栽培人参中皂苷合成相关基因的表达有显著影响，但对野生人参皂苷合成相关基因表达影响不大。本研究通过揭示栽培人参的驯化模式，阐述人参驯化的分子机制，对人参的遗传改良和种植开发具有重要的指导意义。同时拓展了人参根际微生物多样性的知识谱系，为解决人参及人参属其他作物可持续发展提供了思路，同时解析了人参皂苷和多糖生物合成调控网络。