Genome-Wide Identification of Luffa Sucrose Synthase Genes Reveals LaSUS1-Mediated Sugar Metabolism Boosting Drought Tolerance

Luffa (<i>Luffa acutangula</i>) 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 <i>SUS</i> gene family in luffa remain relatively scarce. In this study, we identified nine <i>LaSUS</i> 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 <i>LaSUS</i> 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 <i>LaSUS</i> genes, with <i>LaSUS1</i> showing marked up-regulation under drought conditions. Furthermore, overexpression experiments in tobacco confirmed that <i>LaSUS1</i> contributed to sugar accumulation, increased antioxidant enzyme activities, and positively regulated drought tolerance in luffa. This comprehensive study not only characterizes the <i>LaSUS</i> gene family and bridges the research gap of <i>SUS</i> genes in luffa but also provides theoretical support for investigating the roles of <i>SUS</i> genes in fruit ripening and abiotic stress responses in luffa.