Biosciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA; Arkansas Forest Resources Center, Division of Agriculture, University of Arkansas, Monticello, AR, 71656, USA.
Biosciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA; Arkansas Forest Resources Center, Division of Agriculture, University of Arkansas, Monticello, AR, 71656, USA.
Plant Physiol Biochem. 2019 Oct;143:1-10. doi: 10.1016/j.plaphy.2019.08.014. Epub 2019 Aug 20.
Internal nitrogen (N) cycling is crucial to N use efficiency. For example, N may be remobilized from older, shaded leaves to young leaves near the apex that receive more direct sunlight, where the N can be used more effectively for photosynthesis. Yet our understanding of the mechanisms and regulation of N transport is limited. To identify relevant transporters in Arabidopsis, fifteen transporter knockout mutants were screened for defects in leaf N export using nitrogen-13 (N) administered as NH gas to leaves. We found that three nitrate/peptide transporter family (NPF) genes were necessary for normal leaf N export under low N but not adequate soil N availability, including AtNPF7.1, which has not been previously characterized. High-throughput phenotyping revealed altered leaf area and chlorophyll fluorescence relative to wild-type plants. High AtNPF7.1 expression in flowers and large flower stalks of Atnpf7.1 mutants in low N suggests that AtNPF7.1 influences leaf N export via sink-to-source feedback, perhaps via a role in sensing plant internal N-status. We also identified previously unreported phenotypes for the mutants of the other two NPF transporters that indicate possible roles in N sensing networks.
氮（N）内循环对 N 利用效率至关重要。例如，N 可能从较老的、受遮蔽的叶子重新分配到靠近顶端的年轻叶子，这些叶子接收更多的直射阳光，N 可以更有效地用于光合作用。然而，我们对 N 运输的机制和调节的理解是有限的。为了鉴定拟南芥中的相关转运蛋白，我们筛选了十五个转运蛋白敲除突变体，以确定在低氮条件下使用氮-13（N）作为 NH 气体处理叶片时叶片 N 输出的缺陷。我们发现，三个硝酸盐/肽转运体家族（NPF）基因在低氮但土壤氮供应充足的情况下对正常叶片 N 输出是必要的，包括以前未被表征的 AtNPF7.1。高通量表型分析显示，与野生型植物相比，叶片面积和叶绿素荧光发生了改变。在低氮条件下，Atnpf7.1 突变体的 AtNPF7.1 表达量高，且在花和大花梗中表达量高，表明 AtNPF7.1 通过源库反馈影响叶片 N 输出，可能通过在感知植物内部 N 状态方面发挥作用。我们还为其他两种 NPF 转运蛋白的突变体鉴定了以前未报道的表型，这表明它们可能在 N 感应网络中发挥作用。
