n nnnSeveral quantitative trait locus analyses have suggested thatgrain yield and nitrogen use efficiency are well correlatedwith nitrate storage capacity and efficient remobilization.This study of the Arabidopsis thaliana nitrate transporter NRT1.7provides new insights into nitrate remobilization. Immunoblots,quantitative RT-PCR, β-glucuronidase reporter analysis,and immunolocalization indicated that NRT1.7 is expressed inthe phloem of the leaf minor vein and that its expression levelsincrease coincidentally with the source strength of the leaf.In nrt1.7 mutants, more nitrate was present in the older leaves,less 15NO3– spotted on old leaves was remobilized intoN-demanding tissues, and less nitrate was detected in the phloemexudates of old leaves. These data indicate that NRT1.7 is responsiblefor phloem loading of nitrate in the source leaf to allow nitratetransport out of older leaves and into younger leaves. Interestingly,nrt1.7 mutants showed growth retardation when external nitrogenwas depleted. We conclude that (1) nitrate itself, in additionto organic forms of nitrogen, is remobilized, (2) nitrate remobilizationis important to sustain vigorous growth during nitrogen deficiency,and (3) source-to-sink remobilization of nitrate is mediatedby phloem.展开▼
机译:ABSTRACTn FONT> TH> TR> TABLE> n
n TOP n <字体颜色= 464c53>抽象 FONT> n 介绍 n 结果 n 讨论 n 方法 n 参考文献 n FONT> TH> TR> TABLE> n nnn几个定量性状基因座分析表明, SUP>谷物产量和氮素利用效率与硝酸盐的储存能力和有效的转运紧密相关。 SUP>对拟南芥硝酸盐转运蛋白NRT1.7 SUP>为硝酸盐的修复提供了新的见解。免疫印迹, SUP>定量RT-PCR,β-葡萄糖醛酸苷酶报道基因分析, SUP>和免疫定位表明 NRT1.7 I>在 SUP中表达>叶片次生静脉的韧皮部及其表达水平 SUP>的增加与叶片的来源强度一致。 SUP>在 nrt1.7 I>突变体中,较老的叶片中存在更多的硝酸盐, SUP>较少的 15 SUP> NO 3 SUB> – SUP> SUP> SUP> N需求组织,在老叶韧皮部 SUP>渗出液中硝酸盐含量较低。这些数据表明,NRT1.7负责 SUP>对源叶中硝酸盐的韧皮部负载,从而使硝酸盐 SUP>从老叶转移到年轻叶中。有趣的是, SUP> nrt1.7 I>突变体在外部氮 SUP>耗尽时显示出生长迟缓。我们得出的结论是:(1)除了有机形式的氮之外,硝酸盐本身也被迁移,(2)硝酸盐迁移 SUP>对于氮缺乏时维持旺盛的生长很重要, SUP> SUP>和(3)韧皮部介导的 SUP>硝酸盐的源到库转移。 SUP>
展开▼
Graduate Institute of Life Sciences, National Defense Medical Center, Taipei 112, Taiwan|Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan;
Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan;
Graduate Institute of Life Sciences, National Defense Medical Center, Taipei 112, Taiwan|Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan;
Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan;
Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan;