Wxlv, the Ancestral Allele of Rice Waxy Gene12.084Changquan Zhang, Jihui Zhu, Shengjie Chen, Xiaolei Fan, Qianfeng Li, Yan Lu, Min Wang1, Hengxiu Yu, Chuandeng Yi, Shuzhu Tang, Minghong Gu, Qiaoquan LiuMolecular Plant, 2019, 12(8): 1157-1166 DOI: 10.1016/j.molp.2019.05.011; 追溯原文......本站官方QQ群：62473826Oryza sativa; Waxy; eating and cooking quality; allelic variation; artificial selectionKey Laboratory of Plant Functional Genomics of the Ministry of Education/Jiangsu Key Laboratory of Crop Genomics and Molecular Breeding, College of Agriculture, Yangzhou University; Co-Innovation Center for Modern Production Technology of Grain Crops of Jiangsu Province/Key Laboratory of Crop Genetics and Physiology of Jiangsu Province, Yangzhou UniversityIn rice grains, the Waxy (Wx) gene is responsible for the synthesis of amylose, the most important determinant for eating and cooking quality. The effects of several Wx alleles on amylose content and the taste of cooked rice have been elucidated. However, the relationship between artificial selection and the evolution of various Wx alleles as well as their distribution remain unclear. Here we report the identification of an ancestral allele, Wxlv, which dramatically affects the mouthfeel of rice grains by modulating the size of amylose molecules. We demonstrated that Wxlv originated directly from wild rice, and the three major Wx alleles in cultivated rice (Wxb, Wxa, and Wxin) differentiated after the substitution of one base pair at the functional sites. These data indicate that the Wxlv allele played an important role in artificial selection and domestication. The findings also shed light on the evolution of various Wx alleles, which have greatly contributed to improving the eating and cooking quality of rice.
水稻Waxy基因的祖先等位基因Wxlv该研究从一个地方籼稻品种中图位克隆了控制稻米高直链淀粉、低粘滞性（Low Viscosity, LV）的主效基因，证明该基因为Wx的一个特异等位基因，命名为Wxlv。与控制高直链淀粉含量的Wxa等位基因相比，Wxlv第10外显子一个单碱基差异造成其编码的GBSSI第415残基由丝氨酸变为脯氨酸，改变了该酶的磷酸化，使酶活性明显增强，从而使胚乳中合成更多中短分子量的直链淀粉。这是导致含Wxlv稻米在蒸煮过程中难以彻底糊化而造成低淀粉粘滞性、米饭口感变差的根本原因。进一步研究发现，在具中低直链淀粉含量的Wx等位基因中引入该功能位点，可用于优良食味稻米的培育。
通过对近千份野生稻和栽培稻种质资源中Wx基因序列的遗传多样性和分子序列进化分析，证明Wxlv与野生稻中Wx基因序列及功能基本一致，在进化中属于祖先基因。携带来自野生稻Wx-w单倍型的稻米表现为高直链淀粉含量和低淀粉粘滞特性，米饭口感和食味较差。栽培稻中的秋稻和少数籼稻品种中含有Wx等位基因，而栽培稻中其它Wx等位变异类型都是从其进化或人工选择而来。研究表明，在栽培稻的起源和进化过程中，首先从野生稻的Wx-w单倍型进化为栽培稻中的Wx单倍型，虽然非编码区核苷酸序列发生了一些改变，但仍保留了原有的功能，这类稻米的蒸煮食味品质较差。
栽培稻中的Wxlv等位基因可细分为4种单倍型，现有栽培稻品种中的Wxb和Wxin等位基因分别从第I种Wxlv单倍型中进化而来，而Wxa则来自第II种Wxlv单倍型；粳型软米和籼型软米中的Wxmp或Wxop具有不同的选择路径，分别从Wxb和第IV类Wxlv单倍型经点突变选择产生；绝大多数糯稻中的wx变突都源于Wxb。有趣的是，这些等位基因具有明显的优势地理分布区域，说明人工选择在该基因的演化过程中发挥了重要作用。
►基因列表◄ 颗粒结合型淀粉合酶; 蜡质基因; 糯性基因 wx; OsGBSSI; qGC-6; Wx-mq; Wx-op