Systematic Identification, Evolution and Expression Analysis of the SPL Gene Family in Sugarcane (Saccharum spontaneum)

Sugarcane is an important sugar and energy crop that is widely grown in tropical and subtropical regions worldwide. SPL genes are a type of plant-specific transcription factor and play key roles in plant growth and development. Here, 17 SPL genes were identified from Saccharum spontaneum. A phylogenetic analysis of 72 SPLs from four species showed that the SPL family was divided into six groups and may have originated from at least two different last common ancestors. Comparative gene structure analysis revealed that the SPL family underwent exon gain or loss during evolution. Synteny analysis indicated that segmental duplication mainly contributed to the expansion of the SPL family in sugarcane. Eleven SsSPLs were predicted to have potential miR156 binding sites. Expression pattern analysis showed that the SsSPL gene family was functionally differentiated, besides, there also may be functional redundancy among paralogous SPL genes. SsSPL genes in clade I may be involved mainly in the development of reproductive organs, while SsSPL genes in clade VI, including SsSPL13, SsSPL1 and SsSPL16, participate predominantly in the development of various tissues during the vegetative growth stage. These results lay a foundation for further functional analysis of SPL in sugarcane.