Natural variation in seed dormancy is controlled by multiple genes mapped as quantitative trait loci in major crop or model plants. This research aimed to clone and characterize the Seed Dormancy1-2 (qSD1-2) locus associated with endosperm-imposed dormancy and plant height in rice (Oryza sativa). qSD1-2 was delimited to a 20-kb region, which contains OsGA20ox2 and had an additive effect on germination. Naturally occurring or induced loss-of-function mutations of the gibberellin (GA) synthesis gene enhanced seed dormancy and also reduced plant height. Expression of this gene in seeds (including endospermic cells) during early development increased GA accumulation to promote tissue morphogenesis and maturation programs. The mutant allele prevalent in semidwarf cultivars reduced the seed GA content by up to 2-fold at the early stage, which decelerated tissue morphogenesis including endosperm cell differentiation, delayed abscisic acid accumulation by a shift in the temporal distribution pattern, and postponed dehydration, physiological maturity, and germinability development. As the endosperm of developing seeds dominates the moisture equilibrium and desiccation status of the embryo in cereal crops, qSD1-2 is proposed to control primary dormancy by a GA-regulated dehydration mechanism. Allelic distribution of OsGA20ox2, the rice Green Revolution gene, was associated with the indica and japonica subspeciation. However, this research provided no evidence that the primitive indica- and common japonica-specific alleles at the presumably domestication-related locus functionally differentiate in plant height and seed dormancy. Thus, the evolutionary mechanism of this agriculturally important gene remains open for discussion.
種子休眠的自然變異受到多個基因的控制，在主要作物或者模式植物中作為數(shù)量性狀位點進行了定位。本文研究旨在克隆并鑒定qSD1-2位點，該位點與水稻的胚乳強制休眠以及株高相關(guān)。qSD1-2定位在20-kb的區(qū)域內(nèi)，包含OsGA20ox2，對于萌發(fā)具有加性效應(yīng)。這個赤霉素（GA）合成基因自然發(fā)生或者誘導(dǎo)的功能缺失突變會增強種子休眠并引起株高變矮。在早期發(fā)育階段，種子中（包括胚乳細胞）這個基因的表達會增加GA積累，進而促進組織的形態(tài)發(fā)生以及發(fā)育成熟過程。在半矮化栽培品種中非常普遍的突變等位基因會將早期階段種子中GA的含量降低多達2倍，這會減緩組織形態(tài)發(fā)生，包括胚乳細胞分化，以時空分布模式遷移延遲脫落酸積累，推遲脫水作用、生理成熟以及發(fā)芽力的發(fā)展。正如谷類作物中發(fā)育種子的胚乳控制水分平衡以及胚的脫水狀態(tài)，我們認為qSD1-2通過GA調(diào)控的脫水作用機制控制主要休眠。水稻綠色革命基因OsGA20ox2等位基因分布與秈稻和粳稻亞種相關(guān)。但是，本文研究沒有提供證據(jù)表明原始秈稻和常規(guī)粳稻等位基因可能馴化相關(guān)位點在株高和種子休眠中的功能差異。因而，這個農(nóng)業(yè)重要基因的進化機制仍需要更廣泛的討論。