SQUAMOSA Promoter Binding Protein-Like (SPL) Gene Family: TRANSCRIPTOME-Wide Identification, Phylogenetic Relationship, Expression Patterns and Network Interaction Analysis in Panax ginseng C. A. Meyer

SPL (SQUAMOSA promoter binding protein-like) gene family is specific transcription factor in the plant that have an important function for plant growth and development. Although the SPL gene family has been widely studied and reported in many various plant species from gymnosperm to angiosperm, there are no systematic studies and reports about the SPL gene family in Panax ginseng C. A. Meyer. In this study, we conducted transcriptome-wide identification, evolutionary analysis, structure analysis, and expression characteristics analysis of SPL gene family in Panax ginseng by bioinformatics. We annotated the PgSPL gene family and found that they might involve in multiple functions including encoding structural proteins, but the main function were still focused on the binding function. The result showed that 106 PgSPL transcripts were classified into two clades - A and B, both of which respectively consisted of three groups. Besides, we profiled PgSPL transcripts’ genotypic, temporal, and spatial expression characteristics. Furthermore, we calculated the correlation of PgSPL transcripts in the 14 tissues of a 4 years old ginseng and 42 farmers’ cultivars farmers’ cultivars of 4 years old ginsengs’ roots with both results showing that SPL transcripts formed a single network, which indicated that PgSPLs inter-coordinated when performing their functions. What’s more, we found that most PgSPL transcripts tended to express in older ginseng instead of younger ginseng, which was not only reflected in the expression of more types of SPL transcripts in older ginseng, but also in the higher expression of SPL transcripts in older ginseng. Additionally, we found that four PgSPL transcripts were only massively expressed in roots. According to PgSPL transcripts’ expression characteristics, we found that PgSPL23-35 and PgSPL24-09 were most proper two transcripts to further study as ginseng age’s molecular marker. These results provide the basis for further elucidation of the PgSPL transcripts’ biological function in ginseng and ginseng genetics improvement and gene breeding in the future.