Comprehensive characterization and expression profiling of sucrose phosphate synthase (SPS) and sucrose synthase (SUS) family in Cucumis melo under the application of nitrogen and potassium.

backgroundSugars are not only important biomacromolecules that play vital roles in plant growth, development and environmental stress tolerance, but they also provide carbon skeletons for the synthesis of other macromolecules, such as proteins and nucleic acids. Sugar-related proteins play key roles in the movement of sugars from source tissues (such as leaves) to sink tissues (such as fruits), ultimately influencing fruit development. However, the evolutionary dynamics of this important sugar-related gene family in the Cucumis melo (C.melo) crop are still unknown, and the functional differentiation of melon genes remains unclear.

resultsTo understand the sucrose metabolism in C. melo we identified the sugar base protein by bioinformatics tools and their expression changes under nitrogen and potassium fertilization. Sucrose phosphate synthase (SPS) and sucrose synthase (SUS) are key sugar-based transfer enzymes that play a vital role in sugar accumulation. However, to date, the evolutionary history and functional characteristics of sugar-related protein in C. melo remain unknown. Therefore, in this work, we investigated six SPS genes and four SUS genes from C. melo, along with the conserved domain of SUS proteins of Arabidopsis thaliana. Phylogeny and structural features demonstrated that SPS and SUS genes were categorized into four subfamilies (I to IV) and had non-uniform form distribution across the seven melon chromosomes. Moreover, the functional divergence between clades was shown by gene structure and conserved motifs. In C.melo, transposed duplication events have been essential to the growth and development of the sugar gene family. Analysis of the upstream regions showed growth-promoting elements that could be targeted to manage various stress conditions through a variety of trans-acting factors involving sugar metabolism. Moreover, the target of microRNAs revealed that miRNAs have a role in the development and control of sugar genes. Furthermore, expression profiling revealed the differential expression of these genes during fruit developmental stages.

conclusionThis work established the foundational knowledge to investigate the function and mechanism of sucrose accumulation in fruit. CLINICAL TRIAL NUMBER: Not applicable.