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Summary: MiRNAs have been reported to be the key regulators involving a wide range of biological processes in diverse plant species, but their functions in switchgrass, an important biofuel and forage crop, are largely unknown. Here, we reported the novel function of miR528, which has expanded to four copies in switchgrass, in controlling biomass trait of tillering number and regrowth rate after mowing. Blocking miR528 activity by expressing short tandem target mimic (STTM) increased tiller number and regrowth rate after mowing. The quadruple pvmir528 mutant lines derived from genome editing also showed such improved traits. Degradome and RNA‐seq analysis, combined with in situ hybridization assay revealed that up‐regulation of two miR528 targets coding for Cu/Zn‐SOD enzymes, might be responsible for the improved traits of tillering and regrowth in pvmir528 mutant. Additionally, natural variations in the miR528‐SOD interaction exist in C3 and C4 monocot species, implying the distinct regulatory strength of the miR528‐SOD module during monocot evolution. Overall, our data illuminated a novel role of miR528 in controlling biomass traits and provided a new target for genetic manipulation‐mediated crop improvement. [ABSTRACT FROM AUTHOR]

Leaves of many plant species open during the day and fold at night. Diurnal leaf movement, named nyctinasty, has been of great interest to researchers since Darwin's time. Nyctinastic leaf movement is generated by the pulvinus, which is a specialized motor organ located at the base of leaf and leaflet. The molecular basis and functional reason behind nyctinasty are unknown., In a forward screening of a retrotransposon-tagged mutant population of Medicago truncatula, four petiolule-like pulvinus ( plp) mutant lines with defects in leaf movement were identified and characterized., Loss of function of PLP results in the change of pulvini to petiolules. PLP is specifically expressed in the pulvinus, as demonstrated by quantitative reverse-transcription polymerase chain reaction analysis, expression analysis of a PLP promoter- β-glucuronidase construct in transgenic plants and in situ hybridization. Microarray analysis revealed that the expression levels of many genes were altered in the mutant during the day and at night. Crosses between the plp mutant and several leaf pattern mutants showed that the developmental mechanisms of pulvini and leaf patterns are likely independent., Our results demonstrated that PLP plays a crucial role in the determination of pulvinus development. Leaf movement generated by pulvini may have an impact on plant vegetative growth. [ABSTRACT FROM AUTHOR]