SPL7 and SPL8 represent a novel flowering regulation mechanism in switchgrass

Abstract

Summary The aging pathway in flowering regulation is controlled mainly by microRNA156 (miR156). Studies in Arabidopsis thaliana reveal that nine miR156‐targeted SQUAMOSA PROMOTER BINDING‐LIKE (SPL) genes are involved in the control of flowering. However, the roles of SPLs in flowering remain elusive in grasses. Inflorescence development in switchgrass was characterized using scanning electron microscopy (SEM). Microarray, quantitative reverse transcription polymerase chain reaction (qRT‐PCR), chromatin immunoprecipitation (ChIP)‐PCR and EMSA were used to identify regulators of phase transition and flowering. Gene function was characterized by downregulation and overexpression of the target genes. Overexpression of SPL7 and SPL8 promotes flowering, whereas downregulation of individual genes moderately delays flowering. Simultaneous downregulation of SPL7/SPL8 results in extremely delayed or nonflowering plants. Furthermore, downregulation of both genes leads to a vegetative‐to‐reproductive reversion in the inflorescence, a phenomenon that has not been reported in any other grasses. Detailed analyses demonstrate that SPL7 and SPL8 induce phase transition and flowering in grasses by directly upregulating SEPALLATA3 (SEP3) and MADS32. Thus, the SPL7/8 pathway represents a novel regulatory mechanism in grasses that is largely different from that in Arabidopsis. Additionally, genetic modification of SPL7 and SPL8 results in much taller plants with significantly increased biomass yield and sugar release.

Comprehensive Analysis of the SBP Family in Blueberry and Their Regulatory Mechanism Controlling Chlorophyll Accumulation

“…These observations indicated that a subset of VcSBP s might be involved in the regulation of chlorophyll accumulation. Previous studies have revealed that SBP family proteins can directly interact with their clients (for example, AtFUL , AtSOC1 , AtDFR , AtAP1 , MdWRKY100 , MaLCYB1.1 , and MaLCYB1.2 , MADS5 , and MADS32 ), thereby regulating diverse biological processes in plants such as flowering, inflorescence formation, biosynthesis of secondary metabolites, root regeneration, and response to stress ( Yamaguchi et al, 2009 ; Gou et al, 2019 ; Ma et al, 2020 ; Zhu et al, 2020 ). However, the targets of SBP proteins associated with chlorophyll accumulation have remained to be found.…”

Comparative analysis of the SPL gene family in five Rosaceae species: Fragaria vesca, Malus domestica, Prunus persica, Rubus occidentalis, and Pyrus pyrifolia

“…SPL genes are very important for plant growth and development, as they regulate the specific downstream gene expression, such as the phase transition from vegetative to reproductive, trichome development, leaf development, fruit ripening, pollen sac development, fertility, plant hormone signaling [ 11 , 12 , 13 ], toxin resistance [ 14 ], copper deficiency response [ 15 ], temperature, salinity, and drought stress tolerance [ 7 , 16 ]. In addition, SPLs are targeted by miR156 family members [ 17 ].…”

Tolerant mechanism of model legume plant Medicago truncatula to drought, salt, and cold stresses

“…In Arabidopsis, AtSPL9 (squamosa promoter binding protein-like) controls the initiation of cauline leaf axillary meristems (Tian et al, 2014). In transgenic M. truncatula plants overexpressing MtSPL8 inhibits branching by directly suppressing axillary bud formation (Gou et al, 2018). Down-regulation MsSPL8 increases branch density and enhances drought and salt tolerance in transgenic alfalfa (Gou et al, 2018).…”

“…In transgenic M. truncatula plants overexpressing MtSPL8 inhibits branching by directly suppressing axillary bud formation (Gou et al, 2018). Down-regulation MsSPL8 increases branch density and enhances drought and salt tolerance in transgenic alfalfa (Gou et al, 2018). Interestingly, M. truncatula plants with upregulated MtRAV3 (related to ABI3/VP1 transcription factor) have the similar tolerance to drought and salt stress, but exhibiting dwarfing, late flowering, and smaller leaves (Wang S. et al, 2021).…”

“…Salt stress causes osmotic stress, ion toxicity, and oxidative damage to M. truncatula plants, resulting in reduced photosynthesis and biomass (Yousfi et al, 2010;Arraouadi et al, 2012;Luo et al, 2016;Gou et al, 2018;Zhang X. X. et al, 2019;Wang S. et al, 2021). M. truncatula minimizes these damages by regulating the production of osmolytes and antioxidants in cells, the extrusion of Na + out of cells, and the reduction of Na + in leaves (Figure 2).…”