Switchgrass SBP-box transcription factors PvSPL1 and 2 function redundantly to initiate side tillers and affect biomass yield of energy crop

Abstract

BackgroundSwitchgrass (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.ResultsWe 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.ConclusionsOur 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0516-z) contains supplementary material, which is available to authorized users.

Heteroexpression of Osa-miR319b improved switchgrass biomass yield and feedstock quality by repression of PvPCF5

“…For example, overexpression of PvERF001 in switchgrass improved biomass yield and enzymatic saccharification [14]. Suppressing miR156target PvSPL2 activity effectively improved switchgrass biomass yield and lignocellulose conversion [52]. In this study, we show miR319-PvPCF5 regulatory pathway is another option for simultaneously improving biomass yield and enzymatic efficiency.…”

Small RNAs: Big Impact on Plant Development

“…tillering in switchgrass (Panicum virgatum), an important monocot in biofuel production [16]. As engineering plant architecture is an effective approach for increasing plant biomass yield, this study shows the potential relevance of miRNAs in biotechnology applications.…”

Transgenic miR156 switchgrass in the field: growth, recalcitrance and rust susceptibility

“…SPL genes control several biological processes in plants including plant architecture (Preston and Hileman, ). A recent study linked the suppression of PvSPL1 and PvSPL2 genes, both of which are targeted by miR156, to a dramatic increase in tiller number in switchgrass (Wu et al ., ). Accordingly, many of the greenhouse‐grown miR156‐overexpressing lines had lower levels of these two PvSPL genes and significant increases in tiller number relative to the control.…”

“…Most notably, a 9%–21% reduction in the S/G ratio in these two lines was observed across all three seasons (Tables and S2). A recent study showed that the suppression of the miR156‐targeted PvSPL2 gene led to a reduction in lignin content and altered lignin composition in transgenic switchgrass lines (Wu et al ., ). In line with these findings, lignin content and composition were primarily affected in the two lines (T27 and T37) that showed the largest reductions in PvSPL2 expression relative to the other lines and the control (Figures S2 and S3).…”