title: Switchgrass SBP-box transcription factors PvSPL1 and 2 function redundantly to initiate side tillers and affect biomass yield of energy crop.
abstract: BACKGROUND
  Switchgrass (Panicum virgatum L.) is a dedicated lignocellulosic feedstock for bioenergy production. The SQUAMOSA PROMOTER-BINDING PROTEIN (SBP-box)-LIKE transcription factors (SPLs) change plant architecture and vegetative-to-reproductive phase transition significantly, and as such, they are promising candidates for genetic improvement of switchgrass biomass yield. However, the genome-wide identification and functional characterization of SPL genes have yet to be investigated in herbaceous energy crops.
  
  
  RESULTS
  We identified 35 full-length SPL genes in the switchgrass genome. The phylogenetic relationship and expression pattern of PvSPLs provided baseline information for their function characterization. Based on the global overview of PvSPLs, we explored the biological function of miR156-targeted PvSPL1 and PvSPL2, which are closely related members of SPL family in switchgrass. Our results showed that PvSPL1 and PvSPL2 acted redundantly to modulate side tiller initiation, whereas they did not affect phase transition and internode initiation. Consistently, overexpression of the miR156-resistant rPvSPL2 in the miR156-overexpressing transgenic plants greatly reduced tiller initiation, but did not rescue the delayed flowering and increased internode numbers. Furthermore, suppression of PvSPL2 activity in switchgrass increased biomass yield and reduced lignin accumulation, which thereby elevated the total amount of solubilized sugars.
  
  
  CONCLUSIONS
  Our results indicate that different miR156-targeted PvSPL subfamily genes function predominantly in certain biological processes in switchgrass. We suggest that PvSPL2 and its paralogs can be utilized as the valuable targets in molecular breeding of energy crops for developing novel germplasms with high biofuel production.
authors.affiliation: Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 China ; Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 Shandong China.
authors.forename: Zhenying
authors.initials: Z
authors.lastname: Wu
authors.affiliation: Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 China ; Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 Shandong China.
authors.forename: Yingping
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 China ; Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 Shandong China.
authors.forename: Ruijuan
authors.initials: R
authors.lastname: Yang
authors.affiliation: Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 China ; Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 Shandong China.
authors.forename: Tianxiong
authors.initials: T
authors.lastname: Qi
authors.affiliation: Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 China ; Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 Shandong China.
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Hang
authors.affiliation: Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081 China.
authors.forename: Hao
authors.initials: H
authors.lastname: Lin
authors.affiliation: Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 China ; Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 Shandong China.
authors.forename: Gongke
authors.initials: G
authors.lastname: Zhou
authors.affiliation: Forage Improvement Division, The Samuel Roberts Noble Foundation, Ardmore, OK 73401 USA.
authors.forename: Zeng-Yu
authors.initials: ZY
authors.lastname: Wang
authors.affiliation: Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 China ; Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 Shandong China.
authors.forename: Chunxiang
authors.initials: C
authors.lastname: Fu
keywords: Biomass; Energy crop; Lignin; SPL transcription factor; Tiller initiation; Transgenic switchgrass