Medicinal Plant Cultivation Research Center, Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100193, China.
J Integr Plant Biol. 2011 Nov;53(11):879-91. doi: 10.1111/j.1744-7909.2011.01080.x.
Plants develop important regulatory networks to adapt to the frequently-changing availability of copper (Cu). However, little is known about miRNA-associated Cu-regulatory networks in plant species other than Arabidopsis. Here, we report that Cu-responsive miRNAs in Populus trichocarpa (Torr. & Gray) include not only conserved miR397, miR398 and miR408, but also Populus-specific miR1444, suggesting the conservation and diversity of Cu-responsive miRNAs in plants. Copper-associated suppression of mature miRNAs is in company with the up-regulation of their target genes encoding Cu-containing proteins in Populus. The targets include miR397-targeted PtLAC5, PtLAC6 and PtLAC110a, miR398-targeted PtCSD1, PtCSD2a and PtCSD2b, miR408-targeted PtPCL1, PtPCL2, PtPCL3 and PtLAC4, and miR1444-targeted PtPPO3 and PtPPO6. Consistently, P. trichocarpa miR408 promoter-directed GUS gene expression is down-regulated by Cu in transgenic tobacco plants. Cu-response elements (CuREs) are found in the promoters of Cu-responsive miRNA genes. We identified 34 SQUAMOSA-promoter binding protein-like (SPL) genes, of which 17 are full-length PtSPL proteins or partial sequences with at least 300 amino acids. Phylogenetic analysis indicates that PtSPL3 and PtSPL4 are CuRE-binding proteins controlling Cu-responsive gene expression. Cu appears to be not involved in the regulation of these transcription factors because neither PtSPL3 nor PtSPL4 is Cu-regulated and no CuRE exists in their promoters.
植物形成了重要的调控网络以适应铜（Cu）的频繁变化的可利用性。然而，除了拟南芥以外，对于其他植物物种中 miRNA 相关的 Cu 调控网络知之甚少。在这里，我们报道了在杨属（Populus trichocarpa（Torr. & Gray））中 Cu 响应 miRNA 不仅包括保守的 miR397、miR398 和 miR408，还包括杨树特异性的 miR1444，表明了植物中 Cu 响应 miRNA 的保守性和多样性。在杨树中，Cu 相关的成熟 miRNA 抑制与编码含 Cu 蛋白的靶基因的上调有关。这些靶基因包括 miR397 靶向的 PtLAC5、PtLAC6 和 PtLAC110a、miR398 靶向的 PtCSD1、PtCSD2a 和 PtCSD2b、miR408 靶向的 PtPCL1、PtPCL2、PtPCL3 和 PtLAC4，以及 miR1444 靶向的 PtPPO3 和 PtPPO6。一致的是，在转基因烟草植物中，Pt408 启动子指导的 GUS 基因表达被 Cu 下调。Cu 响应 miRNA 基因的启动子中存在 Cu 反应元件（CuREs）。我们鉴定了 34 个 SQUAMOSA 启动子结合蛋白样（SPL）基因，其中 17 个是全长 PtSPL 蛋白或至少 300 个氨基酸的部分序列。系统发育分析表明，PtSPL3 和 PtSPL4 是控制 Cu 响应基因表达的 CuRE 结合蛋白。Cu 似乎不参与这些转录因子的调节，因为 PtSPL3 和 PtSPL4 都不受 Cu 调节，并且它们的启动子中不存在 CuRE。
