水稻粉质胚乳突变体 flo7的理化性质及基因定位

摘要

Starch is major storage substance and accounts for 80% of dry weight in rice endosperm.The rice grain quality is partial determined by component,content and granule structure of starch.In this study,starchy mutant designated flo7 ,selected from the progeny of tissue culture of Nipponbare,displayed floury and opaque endosperm. The grain length of flo7 was longer,but grain width,grain thickness and 1000-grain weight were lower than those of its wild type.Compared with the wild type,the flo7 endosperm accumulated a higher level of glucose,fructose and sucrose,but lower level of dry weight.There was no significant difference in protein content between the wild type and flo7 mutant.The amylose content and gel consistency of flo7 were lower than that of wild type,but the alkali spreading value of flo7 was higher.Scanning electron microscopic examinations showed that the mutant endosperms contained irregular,loosely packed,compound starch granules.Genetic analysis indicated that the mutant phenotype was determined by a single recessive nuclear gene.By means of molecular marker technique,flo7 gene was narrowed down to a 95 .1 kb interval which includes 1 3 open reading frames (ORFs)on the long arm of chromosome 12.The results of RT-PCR indicated that the expression levels of some genes involved in starch synthesis were influenced in flo7 mutant.These results suggested that FLO7 plays an important role in the synthesis and regulation of starch in rice.%淀粉约占水稻胚乳干物质总量的80％,胚乳中淀粉的组分与含量以及颗粒结构决定了稻米品质.从粳稻品种日本晴(Nipponbare)组培后代中获得了一个稳定遗传的粉质胚乳突变体 flo7(floury endosperm 7).该突变体胚乳表现为白色不透明粉质状,同时突变体种子粒长有所增加,而粒宽、粒厚和千粒重均显著降低.与野生型相比,在灌浆过程中突变体flo7籽粒中干物质的积累量减少,而葡萄糖、果糖等游离糖含量增加.突变体 flo7成熟种子的直链淀粉含量和胶稠度显著下降,而碱消值显著增加.胚乳横截面扫描电镜分析发现,突变体 flo7胚乳中淀粉颗粒形状不规则,排列疏松.遗传分析表明 flo7粉质状胚乳突变表型符合单隐性核基因控制的遗传分离规律.以突变体 flo7和南京11杂交衍生的 F2群体为材料,利用简单重复序列(SSR)和插入缺失(Indel)分子标记,将 flo7定位在第12染色体长臂末端 C2-11和 C5-15之间,物理距离为95．1 kb,该区间内包含13个开放阅读框(ORF).在籽粒灌浆过程中利用实时荧光定量 PCR 分析淀粉合成相关基因的表达,发现在突变体中多个淀粉合成相关基因表现出不同程度的上调和下调,表明 FLO7在水稻种子中淀粉的合成与调控中起着重要作用.