Abstract
BackgroundThe SQUAMOSA promoter binding protein-like (SPL) proteins are plant-specific transcription factors (TFs) that function in a variety of developmental processes including growth, flower development, and signal transduction. SPL proteins are encoded by a gene family, and these genes have been characterized in two model grass species, Zea mays and Oryza sativa. The SPL gene family has not been well studied in moso bamboo (Phyllostachys edulis), a woody grass species.ResultsWe identified 32 putative PeSPL genes in the P. edulis genome. Phylogenetic analysis arranged the PeSPL protein sequences in eight groups. Similarly, phylogenetic analysis of the SBP-like and SBP proteins from rice and maize clustered them into eight groups analogous to those from P. edulis. Furthermore, the deduced PeSPL proteins in each group contained very similar conserved sequence motifs. Our analyses indicate that the PeSPL genes experienced a large-scale duplication event ~15 million years ago (MYA), and that divergence between the PeSPL and OsSPL genes occurred 34 MYA. The stress-response expression profiles and tissue-specificity of the putative PeSPL gene promoter regions showed that SPL genes in moso bamboo have potential biological functions in stress resistance as well as in growth and development. We therefore examined PeSPL gene expression in response to different plant hormone and drought (polyethylene glycol-6000; PEG) treatments to mimic biotic and abiotic stresses. Expression of three (PeSPL10, −12, −17), six (PeSPL1, −10, −12, −17, −20, −31), and nine (PeSPL5, −8, −9, −14, −15, −19, −20, −31, −32) genes remained relatively stable after treating with salicylic acid (SA), gibberellic acid (GA), and PEG, respectively, while the expression patterns of other genes changed. In addition, analysis of tissue-specific expression of the moso bamboo SPL genes during development showed differences in their spatiotemporal expression patterns, and many were expressed at high levels in flowers and leaves.ConclusionsThe PeSPL genes play important roles in plant growth and development, including responses to stresses, and most of the genes are expressed in different tissues. Our study provides a comprehensive understanding of the PeSPL gene family and may enable future studies on the function and evolution of SPL genes in moso bamboo.
Highlights
The SQUAMOSA promoter binding protein-like (SPL) proteins are plant-specific transcription factors (TFs) that function in a variety of developmental processes including growth, flower development, and signal transduction
Differential expression profiling of SPL genes in moso bamboo tissues In order to study the dynamics of PeSPL gene expression, we examined the gene expression profiles in different organs using high-throughput RNA sequencing (RNA-seq), which is a next-generation sequencing technology that provides a snapshot of gene expression profiles and mRNA levels at a given time [65, 66]
We systematically analyzed the 32 predicted PeSPL genes, including their gene structure, phylogeny, conserved motifs, promoter regions, gene duplication, and expression profiling, which may be related to their biological functions
Summary
The SQUAMOSA promoter binding protein-like (SPL) proteins are plant-specific transcription factors (TFs) that function in a variety of developmental processes including growth, flower development, and signal transduction. SPL proteins are encoded by a gene family, and these genes have been characterized in two model grass species, Zea mays and Oryza sativa. The SPL gene family has not been well studied in moso bamboo (Phyllostachys edulis), a woody grass species. Moso bamboo is usually characterized by rapid growth and a long vegetative period before flowering [2]. The two SPL genes (AmSBP1 and AmSBP2) first isolated from the snapdragon, Antirrhinum majus, were identified based on their direct interaction with a promoter sequence motif in SQUAMOSA, a floral meristem identity gene [4]. AtSPL3 binds to a conserved cis-element in the promoter region of APETALA1, a floral meristem identity gene that is an ortholog of SQUA, similar to the snapdragon genes AmSBP1 and AmSBP2 [6]
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