School of Life Sciences and Center for Soybean Research of the State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, HKSAR, Hong Kong.
State Key Laboratory of Agrobiotechnology, MOA Key Laboratory of Soil Microbiology, Rhizobium Research Center, and College of Biological Sciences, China Agricultural University, Beijing, China.
Plant Genome. 2021 Jul;14(2):e20103. doi: 10.1002/tpg2.20103. Epub 2021 May 10.
MicroRNAs (miRNAs) are important regulators of biological functions in plants. To find out what roles miRNAs play in regulating symbiotic nitrogen fixation (SNF) in soybean [Glycine max (L.) Merr.], we identified high-confidence differentially expressed (DE) miRNAs from uninoculated roots (UR), rhizobium-inoculated roots (IR), and nodules (NODs) of soybean by robust small RNA sequencing (sRNA-seq). Based on their predicted target messenger RNAs (mRNAs), the expression profiles of some of these DE miRNAs could be linked to nodule functions. In particular, several miRNAs associated with nutrient transportation genes were differentially expressed in IRs and mature NODs. MiR399b, specifically, was highly induced in IRs and NODs, as well as by inorganic phosphate (Pi) starvation. In composite soybean plants overexpressing miR399b, PHOSPHATE2 (PHO2), a known target of miR399b that inhibits the activities of high-affinity Pi transporters, was strongly repressed. In addition, the overexpression of miR399b in the roots of transgenic composite plants significantly improved whole-plant Pi and ureide concentrations and the overall growth in terms of leaf node numbers and whole-plant dry weight. Our findings suggest that the induction of miR399b in NODs could enhance nitrogen fixation and soybean growth, possibly via improving Pi uptake to achieve a better Pi-nitrogen balance to promote SNF in nodules.
MicroRNAs (miRNAs) 在植物的生物功能调节中起着重要作用。为了研究 miRNA 在调控大豆[Glycine max (L.) Merr.]共生固氮(SNF)中的作用，我们通过稳健的小 RNA 测序(sRNA-seq)从未接种根(UR)、根瘤菌接种根(IR)和大豆根瘤中鉴定出高可信度的差异表达(DE)miRNA。根据其预测的靶信使 RNA(mRNA)，这些 DE miRNA 的一些表达谱可能与根瘤功能有关。特别是，一些与营养运输基因相关的 miRNA 在 IR 和成熟根瘤中差异表达。特别是 miR399b 在 IR 和根瘤中高度诱导表达，同时对无机磷(Pi)饥饿也有诱导作用。在过表达 miR399b 的复合大豆植株中，PHOSPHATE2 (PHO2)，miR399b 的一个已知靶基因，抑制高亲和力 Pi 转运体的活性，被强烈抑制。此外，过表达 miR399b 在转基因复合植物的根部显著提高了全株 Pi 和脲浓度以及整株干重的节点数和整株干重。我们的研究结果表明，miR399b 在根瘤中的诱导可能增强氮固定和大豆生长，可能是通过提高 Pi 摄取来实现更好的 Pi-氮平衡，从而促进根瘤中的 SNF。
