水稻胚乳粉质突变体flo9的表型分析和基因定位

Phenotyping and gene-mapping of a floury endosperm mutant flo9 in rice

[目的]淀粉是水稻的主要成分,其含量、组成和结构对稻米品质至关重要,因此,对淀粉合成及调控路径的进一步解析将有助于稻米品质的改良。[方法]从60Co辐射诱变的‘N22’突变体库中筛选获得一份粉质、皱缩、纯合致死的突变体flo9,分析了其形态学特征和理化性质,利用扫描电镜和半薄切片技术观察胚乳内部结构;配制flo9和‘滇粳优1号’的F2群体,并挑选粉质极端个体进行定位;利用qRT-PCR分析淀粉合成相关基因的表达模式。[结果]与野生型相比,flo9突变体的千粒质量、粒长、粒宽、粒厚、直链淀粉含量和脂肪含量均显著降低,而总淀粉含量无显著差异。突变体中淀粉消减值、回复值和崩解值以及米粉在尿素溶液中的溶解能力低于野生型。突变体中造粉体多为圆形或椭圆形,单粒淀粉颗粒增多,造粉体之间排列疏松。利用314个粉质极端个体将FLO9定位在第9染色体长臂123 kb的区间内,该区间包含13个开放阅读框(ORFs)。qRT-PCR分析发现多个淀粉合成和脂质合成相关基因出现不同程度的表达变化。[结论]FLO9参与调控胚乳中淀粉和脂质的合成以及造粉体的发育,为FLO9的克隆和功能解析奠定了基础。

[Objectives]Starch is a major component of rice.The content,composition and fine structure of starch are crucial to the rice quality.Therefore,it is of great significance to dissect the molecular mechanisms underlying starch synthesis pathway and its regulation.[Methods]In this study,we obtained a stably inherited floury endosperm mutant flo9 from‘N22’mutant library induced by 60 Co radiation,with slightly shrunken and homozygous lethal.The morphological characters and the physicochemical properties were analyzed.The endosperm structure was observed by scanning electron microscopy and semi-thin section technology.An F2 population of flo9 mutant and‘Dianjingyou 1’were prepared,and the floury individuals were selected for gene-mapping.The expression patterns of starch synthesis genes were analyzed by qRT-PCR.[Results]Compared to the wild type,the 1 000-grain weight,grain length,grain width,grain thickness,amylose content,and lipid content of the flo9 mutant all extremely decreased,while the total starch content had no change.The SBV(setback),CSV(consistance),BDV(breakdown)and the swelling power of starch of flo9 mutant were lower than the wild type.The starch grains in flo9 mutant significantly decreased in section area,were rounder and loosely packed.flo9 was narrowed down to a 123 kb region on the long-arm of chromosome 9 with 314 recessive individuals.This region contains 13 open reading frames(ORFs).qRT-PCR analysis showed that the expression level of many genes related to starch synthesis and lipid synthesis were changed.[Conclusions]flo9 was involved in starch and lipid biosynthesis in rice developing endosperm,as well as in amyloplast development.This study lays a foundation for the cloning and functional characterization of flo9 in rice.