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《PNAS》:我科學家發現新型水稻抗旱基因 
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發布時間:2013-10-16

10月14日,《美國科學院院刊》(PNAS)在線發表了我國水稻科學家的最新科研成果。在這篇題為“一個關鍵巨型酶DWA1通過調節干旱誘導的表皮蠟質合成來控制水稻抗旱適應性”(Putative megaenzyme DWA1 plays essential roles in drought resistance by regulating stress-induced wax deposition in rice)的學術論文中,來自華中農業大學的研究人員鑒別出了一個水稻基因DWA1,證實其通過調控脅迫誘導的植物角質層蠟質(Cuticular wax)累積發揮了至關重要的抗旱作用。這一研究發現或許對于改良農作物品種的抗旱性具有極其重要的意義。

角質層包括蠟質和角質,是覆蓋于陸生植物表面與外界環境接觸的重要保護性障礙物。角質層蠟質在植物抵抗各種生物和非生物脅迫中起著非常重要的作用,如防止水分的非氣孔行丟失,抵抗病菌入侵和防止草食性昆蟲吞食,抵抗紫外輻射和霜凍等非生物逆境的影響等。

水分脅迫通常會導致蠟質積累增加。對于水分脅迫具有抗性的植物一般都有較厚的表皮蠟質。研究表明,逆境誘導的蠟質含量增加,可導致葉水分喪失的敏感性降低。同時,蠟質含量的增加,同樣可增加植物抗干旱的能力。但目前對于干旱脅迫條件下角質層蠟質累積的遺傳調控機制還不是很清楚。

研究人員鑒別出了一個水稻基因Drought-Induced Wax Accumulation 1 (DWA1),證實它編碼了長度為2391個氨基酸的極大蛋白,該蛋白由多個酶結構構成,其中包括一個氧化還原酶樣結構域、一個包含AMP結合結構域的原核生物非核糖體肽合成酶樣模體,和一個丙二烯氧化合酶樣結構域,該蛋白保守存在于維管植物中。

dwa1基因敲除(KO)的突變體相對野生型對于干旱脅迫高度敏感。DWA1主要表達于維管組織和表皮層,干旱脅迫可強有力地誘導DWA1表達。這一dwa1突變體干旱脅迫下角質層蠟質累積受損,顯著地改變了植物的角質層蠟質組成,導致植物對干旱敏感性增高。且這一突變體的極長鏈脂肪酸水品降低,而過表達DWA1的植物相比于野生型則極長鏈脂肪酸水平增高。 研究人員證實在干旱條件下,dwa1 KO突變體中許多蠟質相關基因的表達顯著受到抑制。此外,他們還在體外證實,DWA1的AMP結合結構域顯示酶活性激活長鏈脂肪酸形成了酰基CoA (acyl-CoA)。這些結果表明,DWA1通過調控水稻中干旱誘導的角質層蠟質累積控制了抗旱性。

論文摘要:

Drought stress is a major limiting factor for crop production. Cuticular wax plays an important role in preventing water loss from drought stress. However, the genetic control of cuticular wax deposition under drought stress conditions has not been characterized. Here, we identified a rice gene Drought-Induced Wax Accumulation 1 (DWA1) encoding a very large protein (2,391 aa in length) containing multiple enzymatic structures, including an oxidoreductase-like domain; a prokaryotic nonribosomal peptide synthetase-like module, including an AMP-binding domain; and an allene oxide synthase-like domain. This previously unreported putative megaenzyme is conserved in vascular plants. A dwa1 KO mutant was highly sensitive to drought stress relative to the WT. DWA1 was preferentially expressed in vascular tissues and epidermal layers and strongly induced by drought stress. The dwa1 mutant was impaired in cuticular wax accumulation under drought stress, which significantly altered the cuticular wax composition of the plant, resulting in increased drought sensitivity. The mutant had reduced levels of very-long-chain fatty acids, and plants overexpressing DWA1 showed elevated levels of very-long-chain fatty acids relative to the WT. The expression of many wax-related genes was significantly suppressed in dwa1 under drought conditions. The AMP-binding domain exhibited in vitro enzymatic activity in activating long-chain fatty acids to form acyl-CoA. Our results suggest that DWA1 controls drought resistance by regulating drought-induced cuticular wax deposition in rice. This finding may have significant implications for improving the drought resistance of crop varieties.

詳細信息:

http://www.cnrri.cn/zjww/Detail.aspx?id=20024514

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