Exogenous CaCl2 Delays Flesh Softening by Inhibiting the Degradation of Cell Wall in Fresh-Cut Cantaloupe

Flesh softening is closely related to the quality of postharvest produces. Although the use of calcium chloride (CaCl2) has been shown to inhibit fruit softening, the underlying molecular mechanisms have remained unclear. In our present investigation, CaCl2 treatment resulted in an enhancement of cytosolic free Ca2+ and polysaccharide contents, firmness, and the integrity of the cell wall structure, particularly evident in the denser middle lamella of fresh-cut cantaloupe. CaCl2 treatment also inhibited the cell wall degrading enzyme activities and gene expressions. Moreover, CmCAMTA2 could identify and bind to the CG-box structure of CmCellulase, Cmα-Gal3, and Cmβ-Glu12, thereby suppressing their transcription. In conclusion, current findings illustrated that CaCl2 treatment triggered CmCAMTA2-mediated transcriptional suppression on cell wall degrading genes, inhibited the polysaccharide component degradation, and maintained better structure integrity of the cell wall, thereby delaying the flesh softening of fresh-cut cantaloupe.