title: Overexpression of miR156 in switchgrass (Panicum virgatum L.) results in various morphological alterations and leads to improved biomass production.
abstract: Switchgrass (Panicum virgatum L.) has been developed into a dedicated herbaceous bioenergy crop. Biomass yield is a major target trait for genetic improvement of switchgrass. microRNAs have emerged as a prominent class of gene regulatory factors that has the potential to improve complex traits such as biomass yield. A miR156b precursor was overexpressed in switchgrass. The effects of miR156 overexpression on SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) genes were revealed by microarray and quantitative RT-PCR analyses. Morphological alterations, biomass yield, saccharification efficiency and forage digestibility of the transgenic plants were characterized. miR156 controls apical dominance and floral transition in switchgrass by suppressing its target SPL genes. Relatively low levels of miR156 overexpression were sufficient to increase biomass yield while producing plants with normal flowering time. Moderate levels of miR156 led to improved biomass but the plants were non-flowering. These two groups of plants produced 58%-101% more biomass yield compared with the control. However, high miR156 levels resulted in severely stunted growth. The degree of morphological alterations of the transgenic switchgrass depends on miR156 level. Compared with floral transition, a lower miR156 level is required to disrupt apical dominance. The improvement in biomass yield was mainly because of the increase in tiller number. Targeted overexpression of miR156 also improved solubilized sugar yield and forage digestibility, and offered an effective approach for transgene containment.
authors.affiliation: Forage Improvement Division, The Samuel Roberts Noble Foundation, Ardmore, OK, USA.
authors.forename: Chunxiang
authors.initials: C
authors.lastname: Fu
authors.forename: Ramanjulu
authors.initials: R
authors.lastname: Sunkar
authors.forename: Chuanen
authors.initials: C
authors.lastname: Zhou
authors.forename: Hui
authors.initials: H
authors.lastname: Shen
authors.forename: Ji-Yi
authors.initials: JY
authors.lastname: Zhang
authors.forename: Jessica
authors.initials: J
authors.lastname: Matts
authors.forename: Jennifer
authors.initials: J
authors.lastname: Wolf
authors.forename: David G J
authors.initials: DG
authors.lastname: Mann
authors.forename: C Neal
authors.initials: CN
authors.lastname: Stewart
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Tang
authors.forename: Zeng-Yu
authors.initials: ZY
authors.lastname: Wang
mesh_terms: D018533:Biomass; D002241:Carbohydrates / Q000096:biosynthesis; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D006868:Hydrolysis; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D012275:Oryza / Q000235:genetics*; D008897:Panicum / Q000033:anatomy & histology* / Q000235:genetics / Q000254:growth & development*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012995:Solubility
chemical_list: D002241:Carbohydrates; D035683:MicroRNAs; D010940:Plant Proteins; D012333:RNA, Messenger