Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China; Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, Hunan Provincial Key Laboratory of Nutrition in Common University, National Engineering Laboratory on Soil and Fertilizer Resources Efficient Utilization, Changsha, China.
National Center of Oilseed Crops Improvement, Hunan Branch, Changsha, China.
Plant Physiol Biochem. 2020 May;150:90-98. doi: 10.1016/j.plaphy.2020.02.034. Epub 2020 Feb 27.
Although WRKY transcription factors (TFs) are known to be involved in the regulation of plant root development, the mechanisms by which these TFs regulate plant tolerance to ammonium (NH) toxicity remain unclear. To identify the molecular mechanisms underlying NH-induced repression of primary root growth and NH sensitivity in Arabidopsis, wild-type (Col-0) and mutant (wrky23) plants were treated with 10 mM KNO (control) or 5 mM (NH)SO (NH toxicity) for 7 days. Under NH toxicity, the fresh weight of wrky23 mutant was significantly lower than that of Col-0 plants, and the NH concentration in wrky23 roots was significantly higher than that in Col-0 roots. However, we observed no significant differences between the two genotypes under the control treatment. Ammonium transporter AMT1;2 expression was induced in wrky23 roots but not in Col-0 roots. The transcript levels of cytosolic glutamine synthetase-encoding genes and activity of glutamine synthetase did not differ significantly between wrky23 and Col-0. Furthermore, the fluorescence and staining patterns of DR5::GFP and DR5::GUS, respectively, were more pronounced under NH toxicity than under the control treatment. Collectively, our results indicate that AMT1;2 expression was induced in the wrky23 mutant in response to NH toxicity, leading to NH accumulation in the roots and primary root growth repression. Under NH toxicity, both auxin transport and distribution were affected, and auxin accumulation in the root tips inhibited primary root growth in the wrky23 mutant. Our study provides important insights into the molecular mechanisms by which WRKY23 TF regulates plant responses to NH toxicity.
虽然 WRKY 转录因子 (TFs) 被认为参与植物根发育的调控，但这些 TFs 调节植物对铵 (NH) 毒性的耐受性的机制尚不清楚。为了鉴定 NH 诱导的拟南芥主根生长抑制和 NH 敏感性的分子机制，用 10 mM KNO（对照）或 5 mM (NH)SO（NH 毒性）处理野生型（Col-0）和突变体（wrky23）植物 7 天。在 NH 毒性下，wrky23 突变体的鲜重明显低于 Col-0 植物，而 wrky23 根中的 NH 浓度明显高于 Col-0 根。然而，在对照处理下，两个基因型之间没有观察到显著差异。AMT1;2 在 wrky23 根中诱导表达，但在 Col-0 根中不诱导表达。细胞质谷氨酰胺合成酶编码基因的转录水平和谷氨酰胺合成酶的活性在 wrky23 和 Col-0 之间没有显著差异。此外，DR5::GFP 和 DR5::GUS 的荧光和染色模式分别在 NH 毒性下比在对照处理下更为明显。总之，我们的结果表明，AMT1;2 在 wrky23 突变体中被诱导以响应 NH 毒性，导致 NH 在根中积累并抑制主根生长。在 NH 毒性下，生长素的运输和分布都受到影响，根尖端生长素的积累抑制了 wrky23 突变体中的主根生长。我们的研究为 WRKY23 TF 调节植物对 NH 毒性的响应的分子机制提供了重要的见解。
