西南糯玉米地方品种waxy基因序列多态性分析

为了解我国西南地区糯玉米和硬粒玉米waxy基因核苷酸多态性, 对23份中国西南玉米地方品种(16份糯玉米和7份硬粒玉米)、2份美洲糯玉米种质的waxy基因第9外显子至第14外显子之间核苷酸序列进行测定, 将所得序列与GenBank中的16份同源序列(来自小颖大刍草、繁茂大刍草和美洲地方栽培品种)进行序列比对。结果表明, 西南糯玉米、西南硬粒玉米和小颖大刍草分别具有14、19和40个多态性位点, 西南糯玉米waxy位点核苷酸多态性为西南硬粒玉米的30%, 是小颖大刍草的14%, Tajima’D检验仅在糯玉米群体D值显著, HKA检验表明waxy位点未受选择作用; 序列比对发现12份西南糯玉米第10外显子同一位置缺失15个核苷酸, 该位点恰为糖基转移酶结构域的起始位置。可见我国糯玉米通过较为独特的突变机制而形成, 在进化过程中经历了驯化瓶颈, 奠基者效应使西南糯玉米waxy位点核苷酸多态性大大降低, 从近缘物种中引入等位变异是改良玉米淀粉质量和产量的关键。

Sequence Polymorphism of waxy Genes in Landraces of Waxy Maize from Southwest China

In order to understand the DNA polymorphism of the waxy genes in waxy maize and flint maize landraces from Southwest China, the 25 sequences from the ninth exon to the fourteenth exon of waxy gene were cloned and sequenced. The sampled landraces included 16 waxy maize cultivars (Zea mays L. ceratina Kulesh.) and seven flint maize cultivars from Southwest China, and tow waxy maize cultivars from Argentina. Additionally we downloaded 16 homologous sequences from six Z. mays subsp. parviglimis individuals, five Z. luxurians individuals and five American landraces from NCBI. The sequences were aligned and DNA variations among them were analyzed. We found waxy maize, flint maize, and parviglumis had 14, 19, and 40 polymorphic sites, respectively. Within the Z. taxa samples, Chinese waxy maize contained 30% of the genetic diversity in Chinese flint maize and 14% of the genetic diversity in Z. mays subsp. parviglimis, respectively. The statistical Tajima’D significance was only found in Chinese waxy maize population. Seventy five percent of the Chinese waxy maize landraces contained one deletion of fifteen nucleotides, which encodes the amino acid sequence NKEAL and is located at the start site of the glycosyl transferases group 1 of waxy gene. Chinese waxy maize might be originated from one special mutant of flint maize and experienced one domestication bottleneck in the process of evolution. The founder effect made the nucleotide diversity of waxy gene in waxy maize lower than that in its relatives. To improve the quality and quantity of starch in maize different alleles from its relatives should be introduced into maize genome.