近期植物學(xué)研究權(quán)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(guó)家重點(diǎn)實(shí)驗(yàn)室龔繼明研究組最新研究成果：擬南芥NRT1.8基因介導(dǎo)的NO3-再分配在植物逆境脅迫耐受機(jī)理中起著重要的調(diào)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(yíng)養(yǎng)物質(zhì),，而且還作為信號(hào)分子在調(diào)控植物的生長(zhǎng)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(huì)長(zhǎng)途轉(zhuǎn)運(yùn)到植物的地上部位進(jìn)行同化,。但是，逆境條件會(huì)促使更多的NO3-留在根部,，這個(gè)生理現(xiàn)象有什么重要的生物學(xué)功能,，其調(diào)控機(jī)制是什么，目前尚不清楚,。
龔繼明研究組通過高通量表達(dá)組技術(shù)和電生理技術(shù),，從擬南芥基因組中克隆到一個(gè)受逆境因子（Cd2＋）和營(yíng)養(yǎng)信號(hào)（NO3-）強(qiáng)烈誘導(dǎo)的基因NRT1.8，該基因編碼一個(gè)pH依賴的內(nèi)向型NO3-低親和轉(zhuǎn)運(yùn)蛋白,，其基本作用在于將木質(zhì)部導(dǎo)管中的NO3-跨木質(zhì)部薄壁細(xì)胞膜轉(zhuǎn)運(yùn)到木質(zhì)部薄壁細(xì)胞中,，從而卸載木質(zhì)部導(dǎo)管中運(yùn)輸?shù)腘O3-，實(shí)現(xiàn)對(duì)NO3-長(zhǎng)途轉(zhuǎn)運(yùn)的調(diào)控,。在鎘脅迫下,，該基因在根中被強(qiáng)烈誘導(dǎo)，導(dǎo)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(dǎo)致植物對(duì)鎘脅迫表現(xiàn)出高度的敏感性,；過量表達(dá)該基因顯著提高了植物對(duì)多種逆境的耐性，進(jìn)一步的研究表明可能是通過重建氮素代謝途徑來實(shí)現(xiàn)的,。這些事實(shí)表明NRT1.8介導(dǎo)的NO3-再分配在植物逆境脅迫耐受機(jī)理中起著重要的調(diào)節(jié)作用,。該成果對(duì)于指導(dǎo)培育礦質(zhì)營(yíng)養(yǎng)高效，尤其是逆境條件下礦質(zhì)營(yíng)養(yǎng)高效的農(nóng)作物具有重要的科學(xué)意義和潛在的應(yīng)用價(jià)值,。
該項(xiàng)工作得到了國(guó)家科技部,、國(guó)家自然科學(xué)基金委、中國(guó)科學(xué)院及上海市的經(jīng)費(fèi)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.
