Regulation of the high-affinity ammonium transporter (BnAMT1;2) in the leaves of Brassica napus by nitrogen status
Regulation of the high-affinity ammonium transporter (BnAMT1;2) in the leaves of Brassica napus by nitrogen status
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DOI：
10.1023/a:1015549115471
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发表时间：
2002-07
影响因子：
5.1
通讯作者：
J. N. Pearson;J. Finnemann;J. Schjoerring
中科院分区：
文献类型：
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作者：
J. N. Pearson;J. Finnemann;J. Schjoerring
甘蓝型油菜叶片质外体中含有大量的NH ~（4+）。用15 NH 4+对离体叶肉原生质体进行生理学研究，发现叶肉原生质体中存在一种高亲和力的铵转运蛋白，该转运蛋白与拟南芥（AtAMT 1;3）中的高亲和力的铵转运蛋白具有生理相似性。PCR技术用于分离aB的全长克隆。与AtAMT 1的同源性为97%;3.当克隆到酵母表达载体pFL 61中时，全长cDNA能够补充不能在以NH 4+作为唯一氮源的培养基上生长的酵母突变体。与离体叶片的监管研究表明，刺激的NH 4+的吸收和mRNA的表达时，叶片提供了不断增加的浓度的NH 4+。连续供NH 4 + 96 h对BnAMT 1; 2 mRNA表达和NH 4+吸收量影响不大，但高NH 4+条件下BnAMT 1; 2 mRNA表达量下降，直接供NH 4+时BnAMT 1; 2 mRNA表达量最高，而直接供谷氨酰胺或谷氨酸时BnAMT 1; 2 mRNA表达量最低，这直接影响同一叶片中叶绿体谷氨酰胺合成酶（GS 2）的活性。这些结果为BnAMT 1; 2在叶片中可能受到与GS 2相似的调控机制提供了初步证据。
Substantial concentrations of NH4+are found in the apoplast of the leaves ofBrassica napus. Physiological studies on isolated mesophyll protoplasts with15NH4+revealed the presence of a high-affinity ammonium transporter that shared physiological similarity to the high-affinity NH4+transporters inArabidopsisthaliana(AtAMT1;3). PCR techniques were used to isolate a full-length clone of aB. napushomologue ofAMT1from shoot mRNA which showed 97% similarity toAtAMT1;3. The full-length cDNA when cloned into the yeast expression vector pFL61 was able to complement a yeast mutant unable to grow on media with NH4+as the sole nitrogen source. Regulatory studies with detached leaves revealed a stimulation of both NH4+uptake and expression of mRNA when the leaves were supplied with increasing concentrations of NH4+. Withdrawal of NH4+supply for up to 96 h had little effect on mRNA expression or NH4+uptake; however, plants grown continuously at high NH4+levels exhibited decreased mRNA expression.BnAMT1;2mRNA expression was highest when NH4+was supplied directly to the leaf and lowest when either glutamine or glutamate was supplied to the leaves, which directly paralleled chloroplastic glutamine synthetase (GS2) activity in the same leaves. These results provide tentative evidence thatBnAMT1;2may be regulated by similar mechanisms to GS2 in leaves.