近期植物學研究權威期刊Plant Cell在線發(fā)表了植物生理生態(tài)研究所植物分子遺傳國家重點實驗室龔繼明研究組最新研究成果：擬南芥NRT1.8基因介導的NO3-再分配在植物逆境脅迫耐受機理中起著重要的調節(jié)作用,。
硝酸根(NO3-)是陸生植物最重要的氮源之一，它不僅是重要的營養(yǎng)物質,，而且還作為信號分子在調控植物的生長發(fā)育過程中發(fā)揮了重要作用,。高等植物通過根系吸收NO3-后，一般會長途轉運到植物的地上部位進行同化,。但是,，逆境條件會促使更多的NO3-留在根部，這個生理現象有什么重要的生物學功能,，其調控機制是什么,，目前尚不清楚。
龔繼明研究組通過高通量表達組技術和電生理技術,，從擬南芥基因組中克隆到一個受逆境因子（Cd2＋）和營養(yǎng)信號（NO3-）強烈誘導的基因NRT1.8,，該基因編碼一個pH依賴的內向型NO3-低親和轉運蛋白，其基本作用在于將木質部導管中的NO3-跨木質部薄壁細胞膜轉運到木質部薄壁細胞中,，從而卸載木質部導管中運輸的NO3-,，實現對NO3-長途轉運的調控。在鎘脅迫下,，該基因在根中被強烈誘導,，導致NO3-留存在植物根中，使得NO3-在植物地上和地下部位的分配比例發(fā)生變化,。在該基因功能缺失突變體中,，這種NO3-的分配方式受到破壞，并由此導致植物對鎘脅迫表現出高度的敏感性,；過量表達該基因顯著提高了植物對多種逆境的耐性,，進一步的研究表明可能是通過重建氮素代謝途徑來實現的。這些事實表明NRT1.8介導的NO3-再分配在植物逆境脅迫耐受機理中起著重要的調節(jié)作用,。該成果對于指導培育礦質營養(yǎng)高效,，尤其是逆境條件下礦質營養(yǎng)高效的農作物具有重要的科學意義和潛在的應用價值。
該項工作得到了國家科技部,、國家自然科學基金委,、中國科學院及上海市的經費支持。(生物谷Bioon.com)
生物谷推薦原文出處：
The Plant Cell doi：10.1105/tpc.110.075242
The Arabidopsis Nitrate Transporter NRT1.8 Functions in Nitrate Removal from the Xylem Sap and Mediates Cadmium Tolerance
Jian-Yong Lia,1, Yan-Lei Fua,1, Sharon M. Pikeb, Juan Baoa, Wang Tianc, Yu Zhanga, Chun-Zhu Chena, Yi Zhanga, Hong-Mei Lia, Jing Huanga, Le-Gong Lic, Julian I. Schroederd, Walter Gassmannb and Ji-Ming Gonga,2
a National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, People's Republic of China
b Division of Plant Sciences, C.S. Bond Life Sciences Center and Interdisciplinary Plant Group, University of Missouri, Columbia, Missouri 65211-7310
c College of Life Sciences, Capital Normal University, Beijing 100037, People's Republic of China
d Division of Biological Sciences and Center for Molecular Genetics, Cell and Developmental Biology Section, University of California, San Diego, California 92093-0116
Long-distance transport of nitrate requires xylem loading and unloading, a successive process that determines nitrate distribution and subsequent assimilation efficiency. Here, we report the functional characterization of NRT1.8, a member of the nitrate transporter (NRT1) family in Arabidopsis thaliana. NRT1.8 is upregulated by nitrate. Histochemical analysis using promoter-β-glucuronidase fusions, as well as in situ hybridization, showed that NRT1.8 is expressed predominantly in xylem parenchyma cells within the vasculature. Transient expression of the NRT1.8:enhanced green fluorescent protein fusion in onion epidermal cells and Arabidopsis protoplasts indicated that NRT1.8 is plasma membrane localized. Electrophysiological and nitrate uptake analyses using Xenopus laevis oocytes showed that NRT1.8 mediates low-affinity nitrate uptake. Functional disruption of NRT1.8 significantly increased the nitrate concentration in xylem sap. These data together suggest that NRT1.8 functions to remove nitrate from xylem vessels. Interestingly, NRT1.8 was the only nitrate assimilatory pathway gene that was strongly upregulated by cadmium (Cd2+) stress in roots, and the nrt1.8-1 mutant showed a nitrate-dependent Cd2+-sensitive phenotype. Further analyses showed that Cd2+ stress increases the proportion of nitrate allocated to wild-type roots compared with the nrt1.8-1 mutant. These data suggest that NRT1.8-regulated nitrate distribution plays an important role in Cd2+ tolerance.
