优质稻米‘青香软粳’低直链淀粉含量形成分子机制的初步研究

Preliminary Study for the Molecular Mechanism of Low Amylose Content in High-Quality Rice (Oryza sativa L.) Variety ‘Qingxiangruanjing’

Waxy(Wx)基因在调控直链淀粉含量形成过程中起着重要的作用,是稻米蒸煮食味品质的一个关键决定因素。在本项研究中,我们以直链淀粉含量为8.7%和10.2%的优质稻品种‘青香软粳’和‘南粳46’为主要研究对象,初步分析并探讨了这两个优质稻品种稻米低直链淀粉形成的分子调控机理。结果显示,虽然都为Wx-II型粳稻品种,‘南粳46’的Wx基因在启动子1773位置存在AA/CT的变异,‘南粳46’和‘青香软粳’的Wx基因在启动子+693位置具有G/A位点多态性。转录水平分析表明,在‘南粳46’和‘青香软粳’稻米发育过程中,Wx基因的表达模式有较大的差异,可能与其启动子序列的多态性相关,AA/CT变异处于Wx基因的转录调控区。Wx基因启动子后+693位点的多态性与已报道Wxmq多态性位点之一相同,引起Arg158/His158的变异;生物信息学软件分析表明,该位点处于底物进入Wx蛋白催化中心的袋口上,Arg158/His158位点的变异可能影响到底物进入Wx蛋白催化活性中心的速率,从而影响稻米直链淀粉的合成过程和含量。文章丰富了Wx基因多态性的研究,为进一步验证其核苷酸变异与稻米直链淀粉含量的相关性奠定了基础。

Waxy （Wx） gene, which is a key factor in regulating amylose content （AC）, plays an important role in determining rice eating and cooking quality （ECQ）. In this study, for further exploiting the underlying relationship and regulatory mechanism between the AC and ECQ, the Wx polymorphism was characterized in the high-quality rice varieties ＇Qingxiangruanjing＇ and ＇Nanjing46＇ with 8.7% and 10.2% AC respectively. Although all of the vari- eties we analyzed belong to the Wx-II japonica cultivars, the AC is different among them. Expression analysis of Wx gene in ＇Qingxiangrnanjing＇ and ＇Nanjing46＇ indicates that their expression patterns are different, which might be correlated to the nucleotide polymorphism at nucleotide position -1 773 from the start codon in ＇Nanjing46＇ variety, and the AA/CT nucleotides locate in the transcription regulatory area. While the Arg^158/His^158 polymor- phism in both ＇Qingxiangruanjing＇ and ＇Nanjing46＇ varieties might have sophisticated effect on AC since the ami-no acid is located in the pocket area of the Wx protein, which may change the catalytic activity of the starch synthase for substrate and affect the AC in rice, and this mutation site also have been reported to be the one of characterizations of the Wx^mq gene. Therefore, our study enriches the research of Wx genetic polymorphism, and provides basis for further validating the relationship between rice AC and Wx gene polymorphism.