Background

The net ammonium fluxes differ among the different root zones of Populus, but the physiological and microRNA regulatory mechanisms are unclear.

Objective

To elucidate the physiological and miRNA regulatory mechanisms, we investigated the two root zones displaying significant differences in net NH₄⁺ effluxes of P. × canescens.

Methods

Populus plantlets were cultivated with 500 μM NH₄Cl for 10 days. Six plants were randomly selected to determine the net NH₄⁺ fluxes using a noninvasive microtest technique. High-throughput sequencing were used to determine the dynamic expression profile of miRNA among the different root zones of Populus.

Results

Net NH₄⁺ efflux in zone I (from 0 to 40 mm from the root apex) was − 19.64 pmol cm⁻² s⁻¹ and in zone II (from 40 to 80 mm) it was − 43.96 pmol cm⁻² s⁻¹. The expression of eleven miRNAs was significantly upregulated, whereas fifteen miRNAs were downregulated. Moreover, eighty-eight target genes of the significantly differentially expressed miRNAs were identified in root zone II compared with zone I. Particularly, ptc-miR171a/b/e and their target, SCL6, were found to be important for the difference in net NH₄⁺ effluxes in the two root zones. Moreover, the expression of the target of ptc-miR169d, NFYA3 was upregulated in root zone II compared with root zone I, contributing to increased NH₄⁺ efflux and decreased NH₄⁺ assimilation in root zone II.

Conclusion

These results indicate that miRNAs regulate the expression levels of their target genes and thus play key roles in net NH₄⁺ fluxes and NH₄⁺ assimilation in different poplar root zones.

中文翻译：

---

杨树铵同化模式不同的两个根区的生理特征和miRNA测序

背景

杨树不同根区的净铵通量不同，但其生理和microRNA调控机制尚不清楚。

客观的

为了阐明生理和 miRNA 调节机制，我们研究了在P.  ×  canescens的净 NH ₄ ^+外排中显示出显着差异的两个根区。

方法

_{用500 μM NH 4 Cl培养}杨树苗10天。随机选择六株植物，使用无创微量测试技术确定净 NH ₄ ^+通量。采用高通量测序技术确定了杨树不同根区中miRNA的动态表达谱。

结果

区域 I（距根尖 0 至 40 mm）中的净 NH ₄ ^{+流出量为 - 19.64 pmol cm -2}  s ^-1，区域 II（从 40 至 80 mm）为 - 43.96 pmol cm ^-2  s ^{- 1} . 11 个 miRNA 的表达显着上调，而 15 个 miRNA 的表达下调。此外，与区域 I 相比，在根区域 II 中鉴定了 88 个显着差异表达的 miRNA 的靶基因。特别是，发现 ptc-miR171a/b/e 及其靶标SCL6对净 NH 的差异很重要₄ ⁺在两个根区流出。此外，ptc-miR169d、NFYA3靶点的表达与根区 I 相比，在根区 II 中上调，导致根区 II 中 NH ₄ ⁺流出增加和 NH ₄ ⁺同化减少。

结论

这些结果表明，miRNA调节其靶基因的表达水平，从而在不同杨树根区的净NH ₄ ⁺通量和NH ₄ ^{+同化中起关键作用。}