Map-Based Cloning of Seed Dormancy1-2 Identified a Gibberellin Synthesis Gene Regulating the Development of Endosperm-Imposed Dormancy in Rice

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Heng Ye, Jiuhuan Feng, Lihua Zhang, Jinfeng Zhang, Muhamad S. Mispan, Zhuanqin Cao, Donn H. Beighley, Jianchang Yang, Xing-You Gu
Plant Physiology, 2015, 169(3): 2152-2165  DOI: 10.1104/pp.15.01202     追溯原文......本站官方QQ群:62473826

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.

qSD1-2图位克隆鉴定了一个赤霉素合成基因,调控水稻胚乳强制休眠的发育

种子休眠的自然变异受到多个基因的控制,在主要作物或者模式植物中作为数量性状位点进行了定位。本文研究旨在克隆并鉴定qSD1-2位点,该位点与水稻的胚乳强制休眠以及株高相关。qSD1-2定位在20-kb的区域内,包含OsGA20ox2,对于萌发具有加性效应。这个赤霉素(GA)合成基因自然发生或者诱导的功能缺失突变会增强种子休眠并引起株高变矮。在早期发育阶段,种子中(包括胚乳细胞)这个基因的表达会增加GA积累,进而促进组织的形态发生以及发育成熟过程。在半矮化栽培品种中非常普遍的突变等位基因会将早期阶段种子中GA的含量降低多达2倍,这会减缓组织形态发生,包括胚乳细胞分化,以时空分布模式迁移延迟脱落酸积累,推迟脱水作用、生理成熟以及发芽力的发展。正如谷类作物中发育种子的胚乳控制水分平衡以及胚的脱水状态,我们认为qSD1-2通过GA调控的脱水作用机制控制主要休眠。水稻绿色革命基因OsGA20ox2等位基因分布与籼稻和粳稻亚种相关。但是,本文研究没有提供证据表明原始籼稻和常规粳稻等位基因可能驯化相关位点在株高和种子休眠中的功能差异。因而,这个农业重要基因的进化机制仍需要更广泛的讨论。


基因列表
  半矮秆基因 sd1; OsGA20ox2; qSD1-2