Abstract
Main conclusionThe function of SQUAMOSA PROMOTER-BINDING PROTEIN-BOX gene TaSPL14 in wheat is similar to that of OsSPL14 in rice in regulating plant height, panicle length, spikelet number, and thousand-grain weight of wheat, but differs during tiller development. TaSPL14 may regulate spike development via ethylene-response gene EIN3-LIKE 1 (TaEIL1), ETHYLENE-RESPONSIVE TRANSCRIPTION FACTOR 2.11 (TaRAP2.11), and ETHYLENE-RESPONSIVE TRANSCRIPTION FACTOR 1 (TaERF1), but not DENSE AND ERECT PANICLE 1 (TaDEP1) in wheat.The SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE gene OsSPL14 from rice is considered to be a major determinant of ideal plant architecture consisting of few unproductive tillers, more grains per spike, and high resistance of stems to lodging. However, the function of its orthologous gene, TaSPL14, in wheat is unknown. Here, we reported the functional similarities and differences between TaSPL14 and OsSPL14. Similar to OsSPL14 knock-outs in rice, wheat TaSPL14 knock-out plants exhibited decreased plant height, panicle length, spikelet number, and thousand-grain weight. In contrast to OsSPL14, however, TaSPL14 did not affect tiller number. Transcriptome analysis revealed that the expression of genes related to ethylene response was significantly decreased in young spikes of TaSPL14 knock-out lines as compared with wild type. TaSPL14 directly binds to the promoters of the ethylene-response genes TaEIL1, TaRAP2.11, and TaERF1, and promotes their expression, suggesting that TaSPL14 might regulate wheat spike development via the ethylene-response pathway. The elucidation of TaSPL14 will contribute to understanding of the molecular mechanisms that underlie wheat plant architecture.
Highlights
The rice SQUAMOSA PROMOTER-BINDING PROTEINLIKE (SPL) gene OsSPL14 encodes a plant-specific transcription factor and is a new "Green Revolution" gene that plays a critical role in regulating rice ideal plant architecture (Wang and Wang 2017; Wang and Zhou 2018; Liu et al 2019)
Because common wheat (BBAADD) is a typical hexaploid species derived from three diploid ancestral species, Triticum urartu (AA), Aegilops speltoides (BB), and Aegilops tauschii (DD) (Petersen et al 2006; Li et al 2015; Ling et al 2018; Zhang et al 2018), the homoeologous genes among these 56 sequences from the three subgenomes were grouped to 19 unique TaSPL genes, 10 of which had been previously isolated and named (Zhang et al 2014)
Similar to OsSPL14, TaSPL14 acts as a major regulator of spike morphology. taspl14 plants showed a reduction in panicle length and spikelet number, but no alterations in panicle branching (Fig. 2c, d)
Summary
The rice SQUAMOSA PROMOTER-BINDING PROTEINLIKE (SPL) gene OsSPL14 ( known as Ideal Plant Architecture 1, IPA1) encodes a plant-specific transcription factor and is a new "Green Revolution" gene that plays a critical role in regulating rice ideal plant architecture (Wang and Wang 2017; Wang and Zhou 2018; Liu et al 2019). Base deletion in the exon of OsSPL14 by gene editing causes a frameshift mutation, and the inactivation of OsSPL14 leads to a dwarf phenotype, with an extremely increased number of tillers, decreased plant height, panicle length, and spikelet number (Li et al 2016). These findings demonstrate that OsSPL14 plays an important role in regulating ideal plant architecture in rice
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