Licorice has been used in traditional Chinese medicine for more than 2000 years. Chalcone isomerase (CHI) is the second rate-limiting enzyme involved in the biosynthetic pathway of flavonoids in licorice. The purpose of this study is to analyze the CHI gene polymorphism and identify CHI haplotypes associated with high/low flavonoid contents. Five Glycyrrhiza uralensis samples with the high flavonoids contents and five Glycyrrhiza inflate samples with low flavonoids contents were selected to clone the CHI cDNA sequences. The CHI haplotypes related to the accumulation of flavonoids were determined and induced to express in Pichia pastoris GS115. Enzymatic reactions and HPLC method were used to verify the functions of the specific CHI haplotypes. 100 CHI cDNA sequences with a full length of 690 bp were obtained and 48 haplotypes were determined. Haplotype 1 and 31 are the major haplotypes in groups with high/low flavonoids contents, respectively. CHI-1 and CHI-31 were successfully expressed and the HPLC results indicated that the catalytical activities of CHI-1 were higher than that of CHI-31. This study analyzed the gene polymorphism of CHI and determined that CHI-1 was conducive to flavonoid biosynthesis. The results of this study will provide a basis for clarifying the function of CHI and further molecular breeding of the high-quality licorice.

欧亚甘草已经在中药中使用了2000多年。查尔酮异构酶（CHI）是甘草中黄酮类化合物生物合成途径中的第二种限速酶。这项研究的目的是分析CHI基因多态性，并确定与高/低黄酮含量相关的CHI单倍型。选择了5个黄酮含量高的甘草样品和5个黄酮含量低的膨胀甘草样品来克隆CHI cDNA序列。确定与类黄酮积累有关的CHI单倍型并诱导其在巴斯德毕赤酵母中表达GS115。酶促反应和HPLC方法用于验证特定CHI单倍型的功能。获得了全长690 bp的100个CHI cDNA序列，并确定了48个单倍型。单倍型1和31分别是黄酮含量高/低的组中的主要单倍型。成功表达了CHI-1和CHI-31，HPLC结果表明CHI-1的催化活性高于CHI-31。这项研究分析了CHI的基因多态性，并确定CHI-1有助于类黄酮的生物合成。这项研究的结果将为阐明CHI的功能和进一步对优质甘草进行分子育种提供基础。