Comparative analysis of sucrose phosphate synthase (SPS) gene family between Saccharum officinarum and Saccharum spontaneum

Background Sucrose phosphate synthase (SPS) genes play vital roles in sucrose production across various plant species. Modern sugarcane cultivar is derived from the hybridization between the high sugar content speciesSaccharum officinarumand the high stress tolerance speciesSaccharum spontaneum, generating one of the most complex genomes among all crops. The genomics of sugarcane SPS remains under-studied despite its profound impact on sugar yield. Results In the present study, 8 and 6 gene sequences for SPS were identified from the BAC libraries ofS. officinarumandS. spontaneum, respectively. Phylogenetic analysis showed thatSPSDwas newly evolved in the lineage of Poaceae species with recently duplicated genes emerging from theSPSAclade. Molecular evolution analysis based on Ka/Ks ratios suggested that polyploidy reduced the selection pressure ofSPSgenes inSaccharumspecies. To explore the potential gene functions, theSPSexpression patterns were analyzed based on RNA-seq and proteome dataset, and the sugar content was detected using metabolomics analysis. All theSPSmembers presented the trend of increasing expression in the sink-source transition along the developmental gradient of leaves, suggesting that theSPSsare involved in the photosynthesis in bothSaccharum species as their function in dicots. Moreover,SPSsshowed the higher expression inS. spontaneumand presented expressional preference between stem (SPSA) and leaf (SPSB) tissue, speculating they might be involved in the differentia of carbohydrate metabolism in these twoSaccharumspecies, which required further verification from experiments. Conclusions SPSAandSPSBgenes presented relatively high expression and differential expression patterns between the twoSaccharumspecies, indicating these twoSPSsare important in the formation of regulatory networks and sucrose traits in the twoSaccharumspecies.SPSBwas suggested to be a major contributor to the sugar accumulation because it presented the highest expressional level and its expression positively correlated with sugar content. The recently duplicatedSPSD2presented divergent expression levels between the twoSaccharumspecies and the relative protein content levels were highest in stem, supporting the neofunctionalization of theSPSDsubfamily inSaccharum.