Carrera Esther, Holman Tara, Medhurst Anne, Dietrich Daniela, Footitt Steven, Theodoulou Frederica L, Holdsworth Michael J
Crop Performance and Improvement Division, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK.
Plant J. 2008 Jan;53(2):214-24. doi: 10.1111/j.1365-313X.2007.03331.x. Epub 2007 Nov 19.
After-ripening (AR) is a time and environment regulated process occurring in the dry seed, which determines the germination potential of seeds. Both metabolism and perception of the phytohormone abscisic acid (ABA) are important in the initiation and maintenance of dormancy. However, molecular mechanisms that regulate the capacity for dormancy or germination through AR are unknown. To understand the relationship between ABA and AR, we analysed genome expression in Arabidopsis thaliana mutants defective in seed ABA synthesis (aba1-1) or perception (abi1-1). Even though imbibed mutant seeds showed no dormancy, they exhibited changes in global gene expression resulting from dry AR that were comparable with changes occurring in wild-type (WT) seeds. Core gene sets were identified that were positively or negatively regulated by dry seed storage. Each set included a gene encoding repression or activation of ABA function (LPP2 and ABA1, respectively), thereby suggesting a mechanism through which dry AR may modulate subsequent germination potential in WT seeds. Application of exogenous ABA to after-ripened WT seeds did not reimpose characteristics of freshly harvested seeds on imbibed seed gene expression patterns. It was shown that secondary dormancy states reinstate AR status-specific gene expression patterns. A model is presented that separates the action of ABA in seed dormancy from AR and dry storage regulated gene expression. These results have major implications for the study of genetic mechanisms altered in seeds as a result of crop domestication into agriculture, and for seed behaviour during dormancy cycling in natural ecosystems.
后熟（AR）是在干燥种子中发生的一个受时间和环境调控的过程，它决定了种子的萌发潜力。植物激素脱落酸（ABA）的代谢和感知在休眠的起始和维持中都很重要。然而，通过后熟调节休眠或萌发能力的分子机制尚不清楚。为了理解ABA与后熟之间的关系，我们分析了拟南芥种子ABA合成缺陷型（aba1-1）或ABA感知缺陷型（abi1-1）突变体的基因组表达。尽管吸胀的突变体种子没有休眠，但它们表现出由干燥后熟引起的全基因组基因表达变化，这与野生型（WT）种子中发生的变化相当。鉴定出了受干燥种子储存正向或负向调控的核心基因集。每个基因集都包含一个分别编码抑制或激活ABA功能的基因（分别为LPP2和ABA1），从而提示了一种干燥后熟可能调节WT种子后续萌发潜力的机制。将外源ABA应用于后熟的WT种子，并没有使吸胀种子的基因表达模式恢复到新鲜收获种子的特征。结果表明，二次休眠状态恢复了后熟状态特异性的基因表达模式。本文提出了一个模型，将ABA在种子休眠中的作用与后熟和干燥储存调控的基因表达区分开来。这些结果对于研究由于作物驯化进入农业而导致种子中改变了的遗传机制，以及对于自然生态系统中休眠循环期间的种子行为具有重要意义。
