Department of Agronomy, College of Agriculture and Biotechnology, Zijingang Campus, Zhejiang University, Hangzhou, 310058, PR China.
Department of Agronomy, College of Agriculture and Biotechnology, Zijingang Campus, Zhejiang University, Hangzhou, 310058, PR China; Jiangsu Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University, Yangzhou, 225009, PR China.
J Adv Res. 2023 Feb;44:23-37. doi: 10.1016/j.jare.2022.04.001. Epub 2022 Apr 9.
Cadmium (Cd) is one of the most detrimental heavy metal pollutants, seriously affecting crop production and human health. Nucleobase-ascorbic acid transporters (NAT) are widely present in many living organisms including plants, animals and microbes; however, the role of NAT in plant Cd tolerance remains unknown.
To identify Cd-induced miRNAs that target HvNAT2 and to determine the role of this gene and its product in Cd tolerance.
High-throughput-sequencing was used to identify the miRNA expression profile of barley roots in response to Cd stress. Overexpression (OX) and RNAi lines were then constructed for HvNAT2 and comparative transcriptomic analysis was performed to determine the function of this transporter examining its effects on traits such as Cd uptake/flux and translocation, morphology and antioxidant capacity in relation to Cd tolerance. In addition, phylogenetic analysis was performed to obtain insights into the evolution of HvNAT2.
Cd stress-induced genome-wide expression profiles of miRNAs identified a Cd-induced miRNA, miR156g-3p_3, that had HvNAT2 as its target. HvNAT2 was negatively regulated in the high-Cd-accumulating and Cd-tolerant genotype Zhenong8. Evolutionary analysis indicated that orthologues of the plasma membrane localized, HvNAT2, can be traced back to the sister group of land plants, the streptophyte algae. Overexpression of HvNAT2 increases Cd tolerance with higher tissue Cd accumulation but less oxidative damage in transgenic barley plants. RNAi of HvNAT2 leads to a significant reduction of Cd tolerance. The higher Cd accumulation in roots of the OX3 line was also demonstrated by confocal microscopy and electrophysiology. Transcriptome analysis showed that the enhancement of antioxidant capacity by HvNAT2 was related to stress signaling pathways. Furthermore, oxidative stress tolerance in HvNAT2-OX plants was regulated by the synthesis of phytochelatins and the glutathione metabolism cycle.
Our study reveals a key molecular mechanism of NAT in Cd tolerance in plants that is useful for sustainable agricultural production and management of hazardous this heavy metal for better environment management and ecosystem function.
镉（Cd）是最具危害性的重金属污染物之一，严重影响作物生产和人类健康。核苷酸碱基-抗坏血酸转运体（NAT）广泛存在于许多生物体中，包括植物、动物和微生物；然而，NAT 在植物 Cd 耐受中的作用尚不清楚。
鉴定 Cd 诱导的靶向 HvNAT2 的 miRNAs，并确定该基因及其产物在 Cd 耐受中的作用。
使用高通量测序技术鉴定大麦根对 Cd 胁迫的 miRNA 表达谱。然后构建 HvNAT2 的过表达（OX）和 RNAi 系，并进行比较转录组分析，以确定该转运体的功能，考察其对 Cd 吸收/通量和转运、形态和抗氧化能力等 Cd 耐受特性的影响。此外，进行系统发育分析以深入了解 HvNAT2 的进化。
Cd 胁迫诱导的 miRNA 全基因组表达谱鉴定出一种 Cd 诱导的 miRNA，miR156g-3p_3，其靶标是 HvNAT2。在高 Cd 积累和 Cd 耐受基因型珍农 8 中，HvNAT2 受到负调控。进化分析表明，定位于质膜的 HvNAT2 直系同源物可以追溯到陆地植物的姐妹群——石松类藻类。HvNAT2 的过表达可提高 Cd 耐受性，同时增加转基因大麦植株的组织 Cd 积累但减少氧化损伤。HvNAT2 的 RNAi 导致 Cd 耐受性显著降低。通过共聚焦显微镜和电生理学也证明了 OX3 系根中 Cd 积累量增加。转录组分析表明，HvNAT2 增强的抗氧化能力与应激信号通路有关。此外，HvNAT2-OX 植物的氧化应激耐受性受植物螯合肽合成和谷胱甘肽代谢循环的调节。
本研究揭示了 NAT 在植物 Cd 耐受中的关键分子机制，对于可持续农业生产和有害重金属的管理具有重要意义，有助于更好的环境管理和生态系统功能。
