12月20日,，美國科學(xué)家在PNAS上發(fā)表了他們最新一項(xiàng)研究成果"Dormancy cycling in Arabidopsis seeds is controlled by seasonally distinct hormone-signaling pathways",，這項(xiàng)研究中，科學(xué)家利用經(jīng)過基因修改的脫落酸受體基因,，制造出了740種脫落酸受體并逐一進(jìn)行了測試,，結(jié)果發(fā)現(xiàn)，有些受體結(jié)合在一起能強(qiáng)化植物的應(yīng)激反應(yīng),，從而提高植物的耐受性,。
當(dāng)植物遭遇干旱天氣時(shí)，它們會(huì)自然產(chǎn)生幫助對(duì)抗干旱環(huán)境的應(yīng)激激素脫落酸。脫落酸是一種抑制生長的植物激素,，因能促使葉子脫落而得名,。它具有控制氣孔關(guān)閉、影響種子發(fā)芽等重要的生理功能,，對(duì)于保護(hù)植物對(duì)抗逆境具有至關(guān)重要的作用,。脫落酸會(huì)開啟植物體內(nèi)的受體，產(chǎn)生包括關(guān)閉葉子上的細(xì)胞以減少水分流失,、讓植物停止生長以減少水分消耗等有用的反應(yīng)來幫助植物存活,。
2009年，鑒于脫落酸受體蛋白在增強(qiáng)植物的耐旱性方面的重要作用,，美國《科學(xué)》雜志將科學(xué)家揭示脫落酸的受體結(jié)構(gòu)這一研究成果列為當(dāng)年的十大科學(xué)突破之一,。
該研究團(tuán)隊(duì)以擬南芥作為實(shí)驗(yàn)對(duì)象，對(duì)其受體基因進(jìn)行了遺傳修改,，結(jié)果發(fā)現(xiàn),，通過修改脫落酸受體可使其能隨時(shí)打開并保持打開狀態(tài)，從而成功增強(qiáng)植物的壓力反應(yīng)通路,。加州大學(xué)河濱分校綜合基因組生物學(xué)研究所的植物生物學(xué)家肖恩·卡特勒解釋道,，每個(gè)應(yīng)激激素受體都有一個(gè)蓋子，可像門一樣打開或關(guān)閉,。當(dāng)受體處于打開狀態(tài)時(shí),，才能誘發(fā)植物的耐旱性。
他們利用修改后的基因制造出了740多種應(yīng)激激素受體并進(jìn)行了逐一測試,，結(jié)果發(fā)現(xiàn),，每種受體“單槍匹馬”只能滿足研究人員的部分需求，但將合適的受體堆積在一起時(shí),，就達(dá)到了理想的效果：受體鎖定在能激活植物體內(nèi)的壓力反應(yīng)通路的這種狀態(tài),。
卡特勒說：“脫落酸受體就是細(xì)胞的指揮，它會(huì)誘導(dǎo)出植物的耐壓性,，現(xiàn)在,，我們洞悉了受體自由演奏這出交響樂的秘密。”最新發(fā)現(xiàn)有望被科學(xué)家們用來對(duì)農(nóng)作物進(jìn)行轉(zhuǎn)基因修改,，以使其在遭遇干旱天氣時(shí),，生存能力更強(qiáng)且產(chǎn)量更高。
科學(xué)家們打算接下來讓這項(xiàng)最新研究成果走出實(shí)驗(yàn)室,，進(jìn)入田間地頭,，不過，他們也表示,，這一過程可能還需要多年,。（生物谷Bioon.com）
doi:10.1073/pnas.1116325108
PMC:
PMID:
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.
