Mannose induces an endonuclease responsible for DNA laddering in plant cells

The effect of D-mannose (Man) on plant cells was studied in two different systems: Arabidopsis roots and maize (Zea mays) suspension-cultured cells. In both systems, exposure to D-Man was associated with a subset of features characteristic of apoptosis, as assessed by oligonucleosomal fragmentation and microscopy analysis. Furthermore, D-Man induced the release of cytochrome c from mitochondria. The specificity of D-Man was evaluated by comparing the effects of diastereomers such as L-Man, D-glucose, and D-galactose. Of these treatments, only D-Man caused a reduction in final fresh weight with concomitant oligonucleosomal fragmentation. Man-induced DNA laddering coincided with the activation of a DNase in maize cytosolic extracts and with the appearance of single 35-kD band detected using an in-gel DNase assay. The DNase activity was further confirmed by using covalently closed circular plasmid DNA as a substrate. It appears that D-Man, a safe and readily accessible compound, offers remarkable features for the study of apoptosis in plant cells.