不同的根区在胡杨属物种中具有不同的吸收**盐（NO₃^-）的能力，但基本的生理和微RNA（miRNA）调节机制仍然未知。

为了解决这个问题，研究了两个具有不同NO3吸收能力的根茎假单胞菌的根区。到根尖的0至40 mm区域（根部区域I）显示出净流入，而40至80 mm的区域（根部区域II）显示出净流出。II区的NO₃^-和铵（NH₄⁺）浓度以及**还原酶（NR）活性低于I区。

与区域I相比，在区域II中鉴定了41个上调的miRNA和23个下调的miRNA，以及这些miRNA的576个靶标。尤其是生长调节因子4（GRF4），即ptc-miR396g-5p和ptc-miR396f_L上调的靶标与区域I相比，区域II中的+ 1R-1被下调，可能有助于区域II中较低的NO3吸收率和吸收。

此外，在根区发现了一些miRNA及其靶标，即C2H2锌指家族成员和APETALA2 /乙烯反应性元素结合蛋白家族成员，这可能在调节NO₃^-吸收中起重要作用。这些结果表明，差异表达的miRNA-靶标对在调节不同NO₃^-吸收速率以及在杨树不同根部区域的同化中起关键作用。

Different root zones have distinct capacities for nitrate (NO₃^-) uptake in Populus species, but the underlying physiological and microRNA (miRNA) regulatory mechanisms remain largely unknown.

To address this question, two root zones of P. × canescens with contrasting capacities forNO₃^- uptake were investigated. The region of 0 to 40 mm (root zone I) to the root apex displayed net influxes, whereas the region of 40 to 80 mm (root zone II) exhibited net effluxes. Concentrations of NO₃^- and ammonium (NH₄⁺) as well as nitrate reductase (NR) activity were lower in zone II than in zone I.

Forty one upregulated and twenty three downregulated miRNAs, and 576 targets of these miRNAs were identified in zone II in comparison with zone I. Particularly, growth-regulating factor 4 (GRF4), a target of upregulated ptc-miR396g-5p and ptc-miR396f_L + 1R-1, was downregulated in zone II in comparison with zone I, probably contributing to lower NO₃^-uptake rates and assimilation in zone II.

Furthermore, several miRNAs and their targets, members of C2H2 zinc finger family and APETALA2/ethylene-responsive element binding protein family, were found in root zones, which probably play important roles in regulating NO₃^- uptake. These results indicate that differentially expressed miRNA-target pairs play key roles in regulation of distinct NO₃^-uptake rates and assimilation in different root zones of poplars.