Abstract
Wheat (Triticum aestivum L.) is one of the most important crops in the world. Squamosa promoter binding protein-like (SPL) proteins are plant-specific transcript factors and play critical roles in plant growth and development. The functions of many SPL gene family members were well characterized in Arabidopsis and rice, in contrast, research on wheat SPL genes is lagging behind. In this study, we cloned and characterized TaSPL16, an orthologous gene of rice OsSPL16, in wheat. Three TaSPL16 homoeologs are located on the short arms of chromosome 7A, 7B, and 7D, and share more than 96% sequence identity with each other. All the TaSPL16 homoeologs have three exons and two introns, with a miR156 binding site in their last exons. They encode putative proteins of 407, 409, and 414 amino acid residues, respectively. Subcellular localization showed TaSPL16 distribution in the cell nucleus, and transcription activity of TaSPL16 was validated in yeast. Analysis of the spatiotemporal expression profile showed that TaSPL16 is highly expressed in young developing panicles, lowly expressed in developing seeds and almost undetectable in vegetative tissues. Ectopic expression of TaSPL16 in Arabidopsis causes a delay in the emergence of vegetative leaves (3–4 days late), promotes early flowering (5–7 days early), increases organ size, and affects yield-related traits. These results demonstrated the regulatory roles of TaSPL16 in plant growth and development as well as seed yield. Our findings enrich the existing knowledge on SPL genes in wheat and provide valuable information for further investigating the effects of TaSPL16 on plant architecture and yield-related traits of wheat.
Highlights
Squamosa promoter binding protein-like (SPL) proteins are a diverse plant-specific transcription factor family, which are characterized by their Squamosa promoter-binding (SBP) domain containing a highly conserved region of 76 amino acid residues and consisting of a bipartite nuclear localization signal (NLS) and a zinc finger motif with two Zn2+-binding sites: Cys-Cys-His-CysWheat TaSPL16 Characterization and Functional Identification and Cys-Cys-Cys-His (Yamasaki et al, 2004; Birkenbihl et al, 2005; Yamasaki et al, 2008)
The cDNA sequence highly homologous to HvSPL16 and OsSPL16 in wheat was amplified by reverse transcriptase-polymerase chain reaction (RT-PCR), cloned into pMD19T vector and 20 clones were randomly chosen to sequence
In order to evaluate the phylogenetic relationship of the TaSPL16 cloned above with those SPLs isolated from wheat and other species, a total of 79 SPLs were used for phylogenetic analysis based on the SBP domain, including 16 from Arabidopsis (Yang et al, 2008), 19 from rice (Xie et al, 2006; Yang et al, 2008), 30 from maize (Hultquist and Dorweiler, 2008), 10 from wheat (Zhang et al, 2014), the TaSPL16 isolated above, and those SPL16 from other cereal crops such as sorghum, barley, millet, and Brachpodium distachyon
Summary
Squamosa promoter binding protein-like (SPL) proteins are a diverse plant-specific transcription factor family, which are characterized by their Squamosa promoter-binding (SBP) domain containing a highly conserved region of 76 amino acid residues and consisting of a bipartite nuclear localization signal (NLS) and a zinc finger motif with two Zn2+-binding sites: Cys-Cys-His-CysWheat TaSPL16 Characterization and Functional Identification and Cys-Cys-Cys-His (Yamasaki et al, 2004; Birkenbihl et al, 2005; Yamasaki et al, 2008). 17 nonredundant SPL genes in Arabidopsis genome and 19 in rice genome were predicted (Cardon et al, 1999; Xie et al, 2006; Yang et al, 2008) These SPL genes vary greatly in their size and gene structure, and different SPL genes contain different exon number, whereas the SBP domains of all these SPLs are encoded by the first and second exons (Guo et al, 2008; Yang et al, 2008). These SPLs are divided into five different groups based on their conserved SBP domains (Zhang et al, 2014)
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