The Role of SlGH9-16 Cellulase in Gynoecium Morphogenesis and Fruit Texture in Tomato

Flower development involves dynamic cell wall changes driven by coordinated synthesis, breakdown, and remodeling processes that support cell division, differentiation, and expansion. Endo-1,4-β-glucanases (EGases or cellulases), belonging to the Glycosyl Hydrolase family 9 (GH9), are key enzymes involved in cell wall disassembly and metabolism, as well as cell expansion and differentiation, fruit ripening, and organ abscission. However, their roles during female reproductive development remain poorly understood. Here, we studied the cellulase SlGH9-16 during gynoecium and fruit development in tomato. Expression profiling of SlGH9-16 and its orthologs AtGH9B2 and AtGH9B13 showed conserved and dynamic spatio-temporal expression patterns in female reproductive organs for these three GH9 members. We also generated CRISPR-Cas9 mutants and overexpression (OE) lines for SlGH9-16 and showed that this enzyme is necessary for normal cellular patterning and morphogenesis of the tomato gynoecium. Furthermore, SlGH9-16 serves as a dose-dependent modifier influencing both fruit architecture and texture, with its loss-of-function significantly extending post-harvest shelf life. FT-IR and HPTLC analyses suggest that these phenotypic changes are correlated with distinct chemical changes in the polysaccharide matrix of the pericarp cell wall. In summary, these findings highlight a role for GH9 cellulases in reproductive development and the importance of endo-1,4-β-glucanases in the morphogenesis of tomato gynoecium and fruit.