Luffa (Luffa acutangula) serves as an important edible, medicinal, and industrial crop. Sucrose synthase (SUS, EC 2.4.1.13) catalyzes sucrose metabolism and facilitates the entry of photosynthetically derived sucrose into metabolic pathways, playing crucial roles in plant growth, development, and stress responses. However, systematic investigations on the SUS gene family in luffa remain relatively scarce. In this study, we identified nine LaSUS family members distributed unevenly across six chromosomes. Their physicochemical properties and evolutionary relationships were systematically elucidated using bioinformatics tools. RNA-seq analysis revealed distinct expression patterns of LaSUS genes during luffa fruit aging, with most genes showing significant down-regulation during this process. Notably, several genes exhibited significant correlations with sucrose content during fruit aging. RT-qPCR analysis demonstrated the drought stress responsiveness of LaSUS genes, with LaSUS1 showing marked up-regulation under drought conditions. Furthermore, overexpression experiments in tobacco confirmed that LaSUS1 contributed to sugar accumulation, increased antioxidant enzyme activities, and positively regulated drought tolerance in luffa. This comprehensive study not only characterizes the LaSUS gene family and bridges the research gap of SUS genes in luffa but also provides theoretical support for investigating the roles of SUS genes in fruit ripening and abiotic stress responses in luffa.

Sucrose phosphate synthase (SPS) is a rate-limiting enzyme in plant sucrose biosynthesis. However, the SPS gene family in luffa remains unidentified, and its functional involvement in sugar metabolism is unexplored. Here, we present the first genome-wide identification and functional analysis of the LaSPSs in luffa. We identified nine LaSPS genes, characterized their physicochemical and evolutionary properties, and analyzed their expression patterns in different tissues and response to ethylene and drought treatments. Nine tandem-duplicated LaSPS genes formed four clusters (T1(1/2), T2(3/4), T3(5/6), T4(7–9)) with conserved architectures. RNA-seq analysis indicated a ubiquitous downregulation of LaSPS genes in senescing luffa, wherein sucrose content correlated significantly with all LaSPS members except LaSPS1/2. Exogenous ethylene substantially repressed LaSPSs transcription, while 1-methylcyclopropene (1-MCP) treatment showed induction. Notably, LaSPS3/4 displayed high activation under drought stress. Functional validation via heterologous expression in tobacco confirmed that LaSPS3/4 positively regulates drought resistance. In summary, this study provides a novel perspective for the in-depth investigation of the molecular evolutionary mechanism of the LaSPS gene family and its biological functions in luffa.