Background Switchgrass (Panicum virgatum L.), a C4 perennial grass, has been recognized as one of the most potentially important lignocellulose biofuel crops. MicroRNA319 (miR319) plays a key role in plant development, abiotic resistance, and cell wall biosynthesis by repressing expression of its target TCP genes. We hypothesized miR319-TCP pathway could play important roles in switchgrass feedstock characteristics for biofuel production, and produced switchgrass transgenic plants overexpressing miR319 (by ectopic expressing Osa-MIR319b gene), blocking miR319 (by overexpressing a target mimicry of miR319/MIM319) and repression of miR319 target gene PvPCF5. Plant phenotype, biomass yield, and feedstock quality of transgenic plants were analyzed. Results Overexpression of miR319 in switchgrass promoted leaf elongation and expansion of transgenic plants, increased plant height, stem diameter, and resulted in a significant increase in plant biomass yield. Transgenic plants overexpressing of miR319 reduced lignin content, showed significantly higher enzymatic hydrolysis efficiency compared to the wild type plant. However, opposite results were observed in the MIM319 plants. Furthermore, suppression of miR319 target gene PvPCF5 activity also reduced lignin content, increased lignin monomer S/G ratio and the proportion of β-O-4 linkages, while significantly improving the sugar production per plant. Quantitative real-time (qRT-PCR) analysis indicated that expression of PvMYB58/63B and PvHCT with predicted TCP binding sites in their promoter regions was negatively regulated by miR319-PvPCF5 module. Conclusions MiR319-PvPCF5 module plays positive roles in regulating biomass yield and quality of switchgrass. It can be utilized as a candidate molecular tool in regulating biomass yield and feedstock quality. The finding could also be transferred to other grasses for forage quality improvement through genetic manipulation.

中文翻译：

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Osa-miR319b 的异表达通过抑制 PvPCF5 提高了柳枝稷的生物量产量和原料质量。

背景 柳枝稷 (Panicum virgatum L.) 是一种 C4 多年生草本植物，已被公认为最具潜力的重要木质纤维素生物燃料作物之一。MicroRNA319 (miR319) 通过抑制其靶 TCP 基因的表达，在植物发育、非生物抗性和细胞壁生物合成中发挥关键作用。我们假设 miR319-TCP 途径可能在用于生物燃料生产的柳枝稷原料特性中发挥重要作用，并产生过表达 miR319（通过异位表达 Osa-MIR319b 基因）、阻断 miR319（通过过表达 miR319/MIM319 的目标模拟）和抑制的柳枝稷转基因植物miR319 靶基因 PvPCF5。分析了转基因植物的植物表型、生物量产量和原料质量。结果 miR319在柳枝稷中的过表达促进了转基因植物的叶片伸长和扩张，增加了株高、茎粗，并导致植物生物量产量显着增加。与野生型植物相比，过表达 miR319 的转基因植物降低了木质素含量，显示出显着更高的酶水解效率。然而，在 MIM319 植物中观察到相反的结果。此外，抑制 miR319 靶基因 PvPCF5 活性还降低了木质素含量，增加了木质素单体 S/G 比和 β-O-4 键的比例，同时显着提高了每株植物的糖产量。定量实时 (qRT-PCR) 分析表明 PvMYB58/63B 和 PvHCT 在其启动子区域中具有预测的 TCP 结合位点的表达受到 miR319-PvPCF5 模块的负调控。结论 MiR319-PvPCF5模块对柳枝稷的生物量产量和品质具有积极的调节作用。它可以用作调节生物质产量和原料质量的候选分子工具。这一发现也可以通过基因操作转移到其他草类以提高草料质量。