PDF(Pubmed)
Abstract：
Pre-harvest sprouting of cereals greatly reduces yield and quality of the grains. Abscisic acid (ABA) is an essential phytohormone for the induction and maintenance of seed dormancy. In this study, the ABA responsive promoter-driven ABA biosynthesis gene system was introduced to common wheat (Triticum aestivum L.) to enhance ABA production in the embryos and pre-harvest sprouting tolerance of the grains. This system consists of a wheat ABA responsive element containing Early-Methionine-labelled (EM) promoter and a sorghum 9-cis-epoxycarotenoid dioxygenase (SbNCED) gene which encodes an ABA biosynthesis rate-limiting enzyme. Twenty-three independent single-insertion lines were obtained, from which five homozygous lines showing various SbNCED expression levels were selected. Correlations were observed between SbNCED expression, ABA accumulation in the embryos and enhanced dormancy levels of the grains. The engineered wheat grains exhibited a few day-delay in germination, which should be effective in reducing pre-harvest sprouting damage. However, the increase in ABA levels in the recombinant grains was moderate, which explains why germination was not completely suppressed. Further analysis indicated a concomitant increase in the expression of the ABA catabolic enzyme gene TaABA8\'OH1 and in the levels of isoleucine-conjugated jasmonic acid, implying the presence of possible negative feedback regulation in the innate system, which should be overcome for future technology development. These findings advance an understanding of the regulatory mechanisms of hormone metabolism in seeds and facilitate the development of pre-harvest sprouting tolerance in cereal grains.
摘要：
谷物的收获前发芽大大降低了谷物的产量和质量。脱落酸（ABA）是诱导和维持种子休眠的必需植物激素。在这项研究中,将ABA响应启动子驱动的ABA生物合成基因系统引入普通小麦（TriticumaestivumL.），以增强胚的ABA产量和收获前的籽粒发芽耐受性。该系统由包含早期甲硫氨酸标记（EM）启动子的小麦ABA响应元件和编码ABA生物合成限速酶的高粱9-顺式环氧类胡萝卜素双加氧酶（SbNCED）基因组成。获得了23条独立的单插入线，从中选择显示各种SbNCED表达水平的五个纯合品系。观察到SbNCED表达之间的相关性，ABA在胚胎中的积累并增强了谷物的休眠水平。工程小麦籽粒在发芽方面表现出几天的延迟，这应该是有效地减少收获前发芽的损害。然而,重组谷物中ABA水平的增加是适度的，这解释了为什么发芽没有被完全抑制。进一步的分析表明ABA分解代谢酶基因TaABA8'OH1的表达和异亮氨酸共轭茉莉酸的水平伴随增加，暗示先天系统中可能存在负反馈调节，这应该为未来的技术发展而克服。这些发现促进了对种子中激素代谢调节机制的理解，并促进了谷物收获前发芽耐受性的发展。
