Knockdown of a Rice Stelar Nitrate Transporter Alters Long-Distance Translocation But Not Root Influx
Knockdown of a Rice Stelar Nitrate Transporter Alters Long-Distance Translocation But Not Root Influx
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水稻星硝酸盐转运蛋白的敲低改变了长距离易位，但不会改变根部流入
DOI：
10.1104/pp.112.204461
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发表时间：
2012-12-01
期刊：
影响因子：
7.4
通讯作者：
Xu, Guohua
中科院分区：
文献类型：
--
作者：
Tang, Zhong;Fan, Xiaorong;Xu, Guohua
众所周知，根的硝酸盐吸收是为了适应植物生长对氮的需求。长距离运输和/或根储存池被认为提供负反馈信号调节根吸收。我们表征了水稻（Oryza sativa ssp.）中属于高亲和力硝酸盐转运蛋白2（NRT 2）家族的血管特异性硝酸盐转运蛋白OsNRT2.3a。japonica 'Nipponbare'）。利用原生质体表达、植物体内启动子-β-葡萄糖醛酸酶测定和原位杂交进行的定位分析表明，OsNRT 2.3a定位于质膜上，主要在硝酸盐供应根的中柱木质部薄壁细胞中表达。通过RNA干扰（RNAi）敲低OsNRT2.3a的表达削弱了木质部的硝酸盐负荷，并在低（0.5mM）硝酸盐供应下降低了植物生长。与野生型相比，RNAi株系在根中含有显着更高的硝酸盐和总氮，而在芽中含有更低的硝酸盐和总氮。整个根中的短期[N-15]NO3-内流（5 min）和根表面的NO3-通量表明，与野生型相比，OsNRT2.3a的敲低不影响根的硝酸盐吸收。RNAi植物的一些根硝酸盐转运蛋白（OsNRT2.3b，OsNRT2.4和OsNAR2.1）的表达没有显着变化，但当植物供应硝酸盐时，nia 1（硝酸还原酶）的转录增加，OsNRT2.1和OsNRT2.2的转录减少。综上所述，数据表明，在水稻中，在低硝酸盐供应水平下，0sNRT2.3a在硝酸盐从根到地上部的远距离运输中起关键作用。
Root nitrate uptake is well known to adjust to the plant's nitrogen demand for growth. Long-distance transport and/or root storage pools are thought to provide negative feedback signals regulating root uptake. We have characterized a vascular specific nitrate transporter belonging to the high-affinity Nitrate Transporter2 (NRT2) family, OsNRT2.3a, in rice (Oryza sativa ssp. japonica 'Nipponbare'). Localization analyses using protoplast expression, in planta promoter-beta-glucuronidase assay, and in situ hybridization showed that OsNRT2.3a was located in the plasma membrane and mainly expressed in xylem parenchyma cells of the stele of nitrate-supplied roots. Knockdown expression of OsNRT2.3a by RNA interference (RNAi) had impaired xylem loading of nitrate and decreased plant growth at low (0.5 mM) nitrate supply. In comparison with the wild type, the RNAi lines contained both nitrate and total nitrogen significantly higher in the roots and lower in the shoots. The short-term [N-15]NO3- influx (5 min) in entire roots and NO3- fluxes in root surfaces showed that the knockdown of OsNRT2.3a in comparison with the wild type did not affect nitrate uptake by roots. The RNAi plants showed no significant changes in the expression of some root nitrate transporters (OsNRT2.3b, OsNRT2.4, and OsNAR2.1), but transcripts for nia1 (nitrate reductase) had increased and OsNRT2.1 and OsNRT2.2 had decreased when the plants were supplied with nitrate. Taken together, the data demonstrate that OsNRT2.3a plays a key role in long-distance nitrate transport from root to shoot at low nitrate supply level in rice.