Genome-Wide Identification and Comprehensive Characterization of Luffa Sucrose Phosphate Synthase Gene Family and Revealing LaSPS3/4’s Role in Drought Resistance

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.