Structure, expression profile, and evolution of the sucrose synthase gene family in peach (Prunus persica)

Sucrose synthase (SUS) has been suggested to play a key role in plant sucrose metabolism with recent studies reporting that a small number of genes encoding different isozymes of Sus exist in most plant species. Despite this, information on genes encoding different isozymes of Sus in peach (Prunus persica) is scanty. In this study, we report the prediction, isolation, structural characteristics, phylogenetic connections and expression outline of six Sus genes in peach (PpSusl to 6). The six PpSus genes were found distributed across scaffolds 1, 3, 5, 7, and 8. Analysis of the exons/introns revealed that PpSus genes contain multiple introns that range from 11 to 13 and displayed a high degree of conservation with corresponding Sus genes in other plant species. The comparative screening of motifs in PpSus proteins indicated high conservation in terms of number, width and order of motifs among PpSus proteins, which indirectly indicates that the six PpSus proteins are indeed members of the SUS family. Phylogenetic analysis revealed that PpSus2 to PpSus4 belonged to group II of the Sus family, PpSus5 and PpSus6 were clustered into group III, and group I contained only one peach gene (PpSus 1) together with members from 10 other plant species. Analysis of expression levels of the six PpSus genes revealed that transcripts of PpSus1 were almost undetectable in leaves and in older phloem, while PpSus2 and PpSus4 were almost undetectable in flowers. The other three PpSus genes appeared differentially expressed in all tissues examined and were detected at different stages of tissue development. The results obtained from this study will be useful in selecting candidate PpSus genes for further functional analysis in the pathway of sucrose metabolism in peach and specifically in characterizing the knockout/knockdown mutants of PpSus genes.