生物谷報(bào)道：眾所周知，“氮”,、“磷酸”,、“鈣”是作物生長的三大營養(yǎng)素。缺乏這些營養(yǎng)素的話,，就不能培育出水稻,、小麥等農(nóng)作物和美麗的蘭花等觀賞性植物。雖然這些營養(yǎng)素都是由植物的根來吸收的，但其具體結(jié)構(gòu)還是一個(gè)謎,。
RIKEN植物科學(xué)研究中心的基礎(chǔ)代謝研究小組與德國霍恩海姆大學(xué)共同合作,，弄清了植物作為氮源，向細(xì)胞內(nèi)吸收土壤中的“氨態(tài)氮”時(shí)銨輸送體的作用,。氨態(tài)氮是由微生物分解土壤中含有動植物遺骸和排泄物的蛋白質(zhì)與尿酸,、尿素等做出的氮源。
在植物的根部,，“AMT1型”銨輸送體選擇性地使銨離子運(yùn)送到細(xì)胞內(nèi),。特別是在氮肥料不足時(shí)，AMT1型銨輸送體就會發(fā)揮這個(gè)作用,。研究小組使用擬南芥的基因剔除植物弄清了4種AMT1型銨輸送體的機(jī)能,，闡明了其中3種是吸收氨態(tài)氮的重要物質(zhì)。這個(gè)成果將對提高作物的氮利用率的技術(shù)開發(fā)起到幫助,，同時(shí),，在改善由于作物吸收不完而使過剩營養(yǎng)素流出田地污染環(huán)境的問題上也將作為一個(gè)有用成果。
這是由RIKEN植物科學(xué)研究中心(主任 筱崎一雄)基礎(chǔ)代謝研究小組的高橋秀樹組長與德國霍恩海姆大學(xué)的Nicolaus von Wiren教授共同研究的成果,。
本研究成果刊登于美國科學(xué)雜志The Plant Cell (8月號),。（援引日本理化學(xué)研究所）
原始出處:
Plant Cell Preview
Published on August 10, 2007; 10.1105/tpc.107.052134
Received April 9, 2007
Returned for revision July 13, 2007
Accepted July 23, 2007
The Organization of High-Affinity Ammonium Uptake in Arabidopsis Roots Depends on the Spatial Arrangement and Biochemical Properties of AMT1-Type Transporters
Lixing Yuan 1, Dominique Loqué 1, Soichi Kojima 1, Sabine Rauch 1, Keiki Ishiyama 2, Eri Inoue 2, Hideki Takahashi 2, and Nicolaus von Wirén 1*
1 Molecular Plant Nutrition, Institute of Plant Nutrition, University of Hohenheim, D-70593 Stuttgart, Germany
2 RIKEN Plant Science Center, Yokohama 230-0045, Japan
* To whom correspondence should be addressed. E-mail: [email protected] .
The AMMONIUM TRANSPORTER (AMT) family comprises six isoforms in Arabidopsis thaliana. Here, we describe the complete functional organization of root-expressed AMTs for high-affinity ammonium uptake. High-affinity influx of 15N-labeled ammonium in two transposon-tagged amt1;2 lines was reduced by 18 to 26% compared with wild-type plants. Enrichment of the AMT1;2 protein in the plasma membrane and localization of AMT1;2 promoter activity in the endodermis and root cortex indicated that AMT1;2 mediates the uptake of ammonium entering the root via the apoplasmic transport route. An amt1;1 amt1;2 amt1;3 amt2;1 quadruple mutant (qko) showed severe growth depression under ammonium supply and maintained only 5 to 10% of wild-type high-affinity ammonium uptake capacity. Transcriptional upregulation of AMT1;5 in nitrogen-deficient rhizodermal and root hair cells and the ability of AMT1;5 to transport ammonium in yeast suggested that AMT1;5 accounts for the remaining uptake capacity in qko. Triple and quadruple amt insertion lines revealed in vivo ammonium substrate affinities of 50, 234, 61, and 4.5 µM for AMT1;1, AMT1;2, AMT1;3, and AMT1;5, respectively, but no ammonium influx activity for AMT2;1. These data suggest that two principle means of achieving effective ammonium uptake in Arabidopsis roots are the spatial arrangement of AMT1-type ammonium transporters and the distribution of their transport capacities at different substrate affinities.
