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PNAS:基因修改脱落酸受体可提高植物耐旱性

来源:中国科技网 2011-12-22 14:08

12月20日,美国科学家在PNAS上发表了他们最新一项研究成果"Dormancy cycling in Arabidopsis seeds is controlled by seasonally distinct hormone-signaling pathways",这项研究中,科学家利用经过基因修改的脱落酸受体基因,制造出了740种脱落酸受体并逐一进行了测试,结果发现,有些受体结合在一起能强化植物的应激反应,从而提高植物的耐受性。

当植物遭遇干旱天气时,它们会自然产生帮助对抗干旱环境的应激激素脱落酸。脱落酸是一种抑制生长的植物激素,因能促使叶子脱落而得名。它具有控制气孔关闭、影响种子发芽等重要的生理功能,对于保护植物对抗逆境具有至关重要的作用。脱落酸会开启植物体内的受体,产生包括关闭叶子上的细胞以减少水分流失、让植物停止生长以减少水分消耗等有用的反应来帮助植物存活。

2009年,鉴于脱落酸受体蛋白在增强植物的耐旱性方面的重要作用,美国《科学》杂志将科学家揭示脱落酸的受体结构这一研究成果列为当年的十大科学突破之一。

该研究团队以拟南芥作为实验对象,对其受体基因进行了遗传修改,结果发现,通过修改脱落酸受体可使其能随时打开并保持打开状态,从而成功增强植物的压力反应通路。加州大学河滨分校综合基因组生物学研究所的植物生物学家肖恩·卡特勒解释道,每个应激激素受体都有一个盖子,可像门一样打开或关闭。当受体处于打开状态时,才能诱发植物的耐旱性。

他们利用修改后的基因制造出了740多种应激激素受体并进行了逐一测试,结果发现,每种受体“单枪匹马”只能满足研究人员的部分需求,但将合适的受体堆积在一起时,就达到了理想的效果:受体锁定在能激活植物体内的压力反应通路的这种状态。

卡特勒说:“脱落酸受体就是细胞的指挥,它会诱导出植物的耐压性,现在,我们洞悉了受体自由演奏这出交响乐的秘密。”最新发现有望被科学家们用来对农作物进行转基因修改,以使其在遭遇干旱天气时,生存能力更强且产量更高。

科学家们打算接下来让这项最新研究成果走出实验室,进入田间地头,不过,他们也表示,这一过程可能还需要多年。(生物谷Bioon.com)

Dormancy cycling in Arabidopsis seeds is controlled by seasonally distinct hormone-signaling pathways

Steven Footitt, Isabel Douterelo-Soler1, Heather Clay, and William E. Finch-Savage2

Seeds respond to environmental signals, tuning their dormancy cycles to the seasons and thereby determining the optimum time for plant establishment. The molecular regulation of dormancy cycling is unknown, but an extensive range of mechanisms have been identified in laboratory experiments. Using a targeted investigation of gene expression over the dormancy cycle of Arabidopsis seeds in the field, we investigated how these mechanisms are seasonally coordinated. Depth of dormancy and gene expression patterns were correlated with seasonal changes in soil temperature. The results were consistent with abscisic acid (ABA) signaling linked to deep dormancy in winter being repressed in spring concurrent with enhanced DELLA repression of germination as depth of dormancy decreased. Dormancy increased during winter as soil temperature declined and expression of ABA synthesis (NCED6) and gibberellic acid (GA) catabolism (GA2ox2) genes increased. This was linked to an increase in endogenous ABA that plateaus, but dormancy and DOG1 and MFT expression continued to increase. The expression of SNF1-related protein kinases, SnrK 2.1 and 2.4, also increased consistent with enhanced ABA signaling and sensitivity being modulated by seasonal soil temperature. Dormancy then declined in spring and summer. Endogenous ABA decreased along with positive ABA signaling as expression of ABI2, ABI4, and ABA catabolism (CYP707A2) and GA synthesis (GA3ox1) genes increased. However, during the low-dormancy phase in the summer, expression of transcripts for the germination repressors RGA and RGL2 increased. Unlike deep winter dormancy, this represson can be removed on exposure to light, enabling the completion of germination at the correct time of year.

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