唐古特大黄次生代谢适应的遗传机制

Secondary metabolism results from the adaptation to environment during a long period of plant evolution. The internal factor of plant adaptation to environment is determined by genes. And the key point of plant adaptation and evolution is the relationship between phenotypic characters and genetic structure. As a perennial herb endemic to Qinghai-Tibetan Plateau, Rheum tanguticum is a good material for adaptation and evolution study. Well known all over the world, R. tanguticum is a famous Chinese medicinal plant. Anthraquinones are important secondary metabolites and active ingredients of R. tanguticum. The study on metabolism of anthraquinones in other Polygonaceae plants is much more thorough and plant polyketide synthase Ⅲ (PKS) is the key enzyme during this process. In this project, as the material, R. tanguticum is studied for the composition characteristic of anthranquinones, single nucleotide variation of PKS genes and population genetic structure as well. By way of candidate-gene association analysis, some gene markers and gene sequences with secondary metabolism are identified. The relationship between adaptation of secondary metabolism and genetic evolution is explored. Besides, all the studies above are ultimately to discuss the genetic mechanism of the adaptation of secondary metabolism. The project will establish the foundation for exploring specific genes in secondary metabolism and its expression and regulation. It will further provide new strategies for good germplasm screening and germplasm resources innovation.

次生代谢是植物在长期进化中对生态环境适应的结果，其适应环境的内在因素是由基因控制的，植物表型性状变异与遗传结构的关联是研究植物适应进化的关键。唐古特大黄是青藏高原特有、多年生草本植物，是研究植物长期进化过程中环境适应的较好材料。大黄是闻名中外的我国大宗药材，蒽醌类化合物是其重要的次生代谢产物及有效成分，其它蓼科植物中蒽醌类化合物的代谢途径研究已比较深入，植物Ⅲ型聚酮化合物合酶（PKS）是其代谢的关键酶。本项目选取唐古特大黄为研究对象，对其蒽醌类组成特征及次生代谢相关基因PKS家系的单核苷酸变异和种群结构进行研究；通过候选基因关联分析，确定与次生代谢相关的基因标记及序列，探讨唐古特大黄次生代谢表型适应与遗传进化的关系，进而分析其次生代谢适应的遗传机制。为进一步发掘次生代谢特异基因及其表达调控、优异种质基因筛选和种质资源创新提供新思路。

次生代谢是植物在长期进化中对生态环境适应的结果，其适应环境的内在因素是由基因控制的，植物表型性状变异与遗传结构的关联是研究植物适应进化的关键。唐古特大黄是青藏高原特有、多年生草本植物，是研究植物长期进化过程中环境适应的较好材料。大黄是闻名中外的我国大宗药材，蒽醌类化合物是其重要的次生代谢产物及有效成分，植物Ⅲ型聚酮化合物合酶（PKS）是其代谢的关键酶。本项目对唐古特大黄蒽醌类组成特征及次生代谢相关基因PKS家系的单核苷酸变异和种群结构进行研究，通过关联分析确定与蒽醌类成分相关的标记及基因位点。主要研究结果如下：.1. ISSR标记表明，唐古特大黄在物种（PPB = 95.09%，He = 0.2683，I = 0.4160）和居群（PPB = 46.15%，He = 0.1719，I = 0.2536）水平均具有较高的遗传多样性，野生居群（PPB = 93.87%，He = 0.2703，I = 0.4186）遗传多样性略高于栽培居群（PPB = 85.14%，He = 0.2478，I = 0.3820）。.2. 5种蒽醌类成分、ISSR分子标记及PKS基因序列分析均表明，唐古特大黄居群内变异大于居群间变异，其变异主要存在于居群内。.3. PKS基因片段排序后长度为675bp，其中变异位点有130处，变异位点百分率为19.26%。居群核苷酸多样性Pi为0.0449。唐古特大黄PKS基因片段区别于其它植物的序列特征有六处。歧点分布和中性检验表明，唐古特大黄经历过大规模的居群近期扩张现象。.4. ISSR标记及PKS序列分析表明，唐古特大黄居群存在连锁不平衡结构。TASSEL软件的MLM程序分别对ISSR标记位点和PKS基因片段位点与5种蒽醌类成分表型性状进行关联分析，发现15个位点与5种蒽醌类成分表型性状显著关联。ISSR位点中，与大黄酸关联的位点有4个，与芦荟大黄素关联的位点有3个，与大黄素和大黄酚关联的位点各有2个，与大黄素甲醚关联的位点1个。各位点对表型变异的解释率在0.0483~0.1116之间，平均值为0.0883。还发现一个ISSR位点同时与多个性状相关联，这表明不同的性状可能受同一位点的调控。找到4个PKS位点与蒽醌类次生代谢成分显著关联，与大黄酸相关的141位点；与大黄素相关的95位点；与大黄酚相关的297位点；与大黄素甲醚关联的21位点。