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高产优质是水稻研究的重要目标,水稻产量由单株穗数、每穗粒数、结实率和千粒重等因素决定,而粒长、粒宽和粒厚是影响千粒重的三要素。本研究中,我们克隆到一个影响水稻粒形的基因OsRAMOSA2,通过遗传转化方法,分别获得了OsRAMOSA2基因表达下调(dsRNAiOsRA2)转基因植株和超表达(pUbi::OsRA2)转基因植株。dsRNAiOsRA2转基因种子长宽比增加,粒厚和千粒重降低;而pUbi::OsRA2转基因种子长宽比减小,粒厚及千粒重增加。利用原位杂交的方法揭示出Os RAMOSA2在未成熟种子的幼胚、胚乳、种皮、背部维管束、珠心表皮、珠心突起处、幼胚内的盾片、胚芽、胚根、胚芽鞘、胚根鞘、外胚芽中均有表达。野生型‘ZH11’种子的胚乳细胞中,淀粉粒呈现多面体,形状均一、排列紧密;而在ds RNAi OsRA2转基因种子中,胚乳细胞的淀粉粒变为球状,排列松散。淀粉合成途径中关键酶类编码基因OsSSIIa、OsGBSSI和OsSSIVb在dsRNAiOsRA2转基因植株中的表达被上调,而在pUbi::OsRA2转基因种子中的表达被下调;pUbi::OsRA2转基因种子中的表观直链淀粉含量(apparent amylose content,AAC)相比‘ZH11’显著降低,而dsRNAiOsRA2转基因种子的AAC显著增加。说明OsRAMOSA2可能通过调控淀粉合成途径中关键基因的表达影响籽粒内直链淀粉的合成积累过程进而正调控粒重。
High yield and good quality are important research targets in rice. The yield of rice is determined by the number of panicle per plant, the number of grains per panicle, seed setting rate and grain weight per plant. The grain length, grain width and grain thickness are the three important factors affecting grain weight. In this study, we cloned a gene OsRAMOSA2 that affects rice grain shape. OsROSA2 gene knockdown (dsRNAiOsRA2) transgenic plants and overexpression (pUbi :: OsRA2) transgenic plants were obtained by genetic transformation. The length-width ratio of dsRNAiOsRA2 transgenic seeds increased, while the grain-thickness and 1000-grain weight decreased. However, the aspect ratio of pUbi :: OsRA2 transgenic seeds decreased and the grain thickness and 1000-grain weight increased. In situ hybridization revealed Os RAMOSA2 immature embryos in the immature embryos, endosperm, seed coat, dorsal vascular bundle, Zhu Xin epidermis, beads heart prominence, immature embryos scutellum, germ, radicle, coleoptile , Radicle sheath, ectoderm are expressed. In the endosperm cells of wild-type ZH11 seed, the starch grains appeared polyhedron with uniform shape and close arrangement. In the dsRNAi OsRA2 transgenic seeds, the starch grains of the endosperm cells became spherical and loosely arranged. OsSSIIa, OsGBSSI and OsSSIVb were up-regulated in dsRNAiOsRA2 transgenic plants but down-regulated in pUbi :: OsRA2 transgenic seeds; apparent linear chains in pUbi :: OsRA2 transgenic seeds Apparent amylose content (AAC) was significantly reduced compared to ’ZH11’, while AAC of dsRNAiOsRA2 transgenic seeds was significantly increased. OsRAMOSA2 may regulate the grain weight by regulating the expression of key genes in starch synthesis pathway and affecting the process of amylose accumulation in grains.