Identification, molecular characterization, and expression analysis of the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) gene family in Betula platyphylla Suk.

Abstract

20 SPL genes were identified in Betula platyphylla Suk., and their sequence features and expression profiles provide useful information for further studies on their function. SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL), a family of plant-specific transcription factors, plays a vital regulatory role in plant growth and development. However, information on SPL genes is largely undefined in Betula platyphylla Suk., an economically important tree species in China. Twenty full-length open read frames of SPL genes in B. platyphylla were identified and designated BplSPL1 to BplSPL20. Phylogenetic analyses showed that the genes were divided into eight groups. In addition, 12 BplSPL genes were suggested to be putative targets of miR156. Tissue-specific expression analysis of BplSPL genes indicated diverse spatiotemporal expression patterns. Most BplSPL genes had high transcription levels in leaves, female inflorescences, and male inflorescences. BplSPLs showed significant differences in male development, indicating that these genes may play different roles in this development process. Most miR156-targeted BplSPLs genes were gradually downregulated as female development progressed, whereas the expression levels of miR156 increased during female inflorescence development. This indicated that the miR156/SPL module plays an important role in female development. We also discussed the possible roles that BplSPL genes may play in leaves. Taken as a whole, these results provide a molecular basis for the further functional study of SPL genes in B. platyphylla and are a supplement to the systematic analysis of SPL genes in forest tree species.