Abstract

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 Populus × canescens (Ait.) Smith. with contrasting capacities for NO₃⁻ uptake were investigated. The region of 0–40 mm (root zone I) to the root apex displayed net influxes, whereas the region of 40–80 mm (root zone II) exhibited net effluxes. Concentrations of NO₃⁻ and ammonium (NH₄⁺) as well as nitrate reductase 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.

中文翻译：

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对比两个杨的硝酸盐同化作用的两个根区的生理特性和RNA测序。

摘要

不同根区具有用于硝酸盐不同容量（NO ₃ ^- ）的摄取在杨物种，但潜在的生理和微小RNA（miRNA）的调节机制在很大程度上仍然未知。为了解决这个问题，史密斯杨（Populus×canescens）的两个根区。对比鲜明的能力以NO ₃ ^-摄取的影响。到根尖的0–40 mm区域（根区I）显示净流入，而40–80 mm的区域（根区II）显示净流出。NO浓度的₃ ^-和铵（NH ₄ ⁺）以及硝酸还原酶的活性在II区中均低于I区。与I区相比，II区中鉴定出了41个上调的miRNA和23个下调的miRNA，并且这些576个miRNA的靶标被确定。特别是，生长调节因子4 （GRF4） ，上调PTC-miR396g-5P和PTC-miR396f_L + 1R-1，被下调在区II中与区域I比较的对象，这可能有助于降低NO ₃ ^-摄取速率和同化在区II中。此外，一些miRNA及其目标，成员C2H2锌指家庭和APETALA2 /乙烯反应元件结合蛋白家族，是在根区，这可能是在调节NO扮演重要的角色找到₃ ^-摄取。这些结果表明，差异表达的miRNA靶标对不同中NO的调控中发挥关键作用的₃ ^-的吸收率和同化杨树不同根区。