Guan Peizhu, Wang Rongchen, Nacry Philippe, Breton Ghislain, Kay Steve A, Pruneda-Paz Jose L, Davani Ariea, Crawford Nigel M
Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093;
Biochimie et Physiologie Moleculaire des Plantes, Institut National de la Recherche Agronomique, Centre National de la Recherche Scientifique, F-34060 Montpellier, France;
Proc Natl Acad Sci U S A. 2014 Oct 21;111(42):15267-72. doi: 10.1073/pnas.1411375111. Epub 2014 Oct 6.
To compete for nutrients in diverse soil microenvironments, plants proliferate lateral roots preferentially in nutrient-rich zones. For nitrate, root foraging involves local and systemic signaling; however, little is known about the genes that function in the systemic signaling pathway. By using nitrate enhancer DNA to screen a library of Arabidopsis transcription factors in the yeast one-hybrid system, the transcription factor gene TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR1-20 (TCP20) was identified. TCP20, which belongs to an ancient, plant-specific gene family that regulates shoot, flower, and embryo development, was implicated in nitrate signaling by its ability to bind DNA in more than 100 nitrate-regulated genes. Analysis of insertion mutants of TCP20 showed that they had normal primary and lateral root growth on homogenous nitrate media but were impaired in preferential lateral root growth (root foraging) on heterogeneous media in split-root plates. Inhibition of preferential lateral root growth was still evident in the mutants even when ammonium was uniformly present in the media, indicating that the TCP20 response was to nitrate. Comparison of tcp20 mutants with those of nlp7 mutants, which are defective in local control of root growth but not in the root-foraging response, indicated that TCP20 function is independent of and distinct from NLP7 function. Further analysis showed that tcp20 mutants lack systemic control of root growth regardless of the local nitrate concentrations. These results indicate that TCP20 plays a key role in the systemic signaling pathway that directs nitrate foraging by Arabidopsis roots.
为了在多样的土壤微环境中竞争养分，植物优先在养分丰富的区域增殖侧根。对于硝酸盐而言，根系觅食涉及局部和系统信号传导；然而，对于在系统信号传导途径中发挥作用的基因却知之甚少。通过在酵母单杂交系统中使用硝酸盐增强子DNA筛选拟南芥转录因子文库，鉴定出了转录因子基因玉米分枝1/类周期蛋白/增殖细胞核抗原因子1-20（TCP20）。TCP20属于一个古老的、植物特有的基因家族，该家族调控地上部、花和胚胎发育，它通过与100多个硝酸盐调控基因中的DNA结合的能力而参与硝酸盐信号传导。对TCP20插入突变体的分析表明，它们在均匀硝酸盐培养基上主根和侧根生长正常，但在分根培养板的异质培养基上优先侧根生长（根系觅食）受损。即使培养基中均匀存在铵，突变体中优先侧根生长的抑制仍然明显，这表明TCP20的反应是针对硝酸盐的。将tcp20突变体与nlp7突变体进行比较，nlp7突变体在根系生长的局部控制方面存在缺陷，但在根系觅食反应方面没有缺陷，这表明TCP20的功能独立于NLP7的功能且与之不同。进一步分析表明，无论局部硝酸盐浓度如何，tcp20突变体都缺乏对根系生长的系统控制。这些结果表明，TCP20在拟南芥根系引导硝酸盐觅食的系统信号传导途径中起关键作用。
