Effect of nitric oxide on the sensitivity of banana fruit slices to ethylene

The effects of nitric oxide (NO) treatment on the sensitivity of banana fruit slices to ethylene were investigated. Fruit slices were partial-pressure infiltrated for 3 min in a NO donor Solution of 5 mM sodium nitroprusside (SNP), followed by treatment with 100 mu l l(-1) ethylene for 24 h, then packed into polyethylene bags and stored for 5 d at 24 degrees C. Control slices were treated with distilled water instead of SNP, then treated with ethylene. Changes in fruit firmness, chlorophyll content, respiration rate, the activities of three cell wall modifying enzymes [polygalacturonase (PG), endo-beta-1,4-glucanase (EGase), and beta-galactosidase (beta-Gal)], and total amylase activity were measured. Expression of the expansin (MaExp1) and ethylene receptor (MaERS2) genes were also analysed. The application of NO, prior to ethylene exposure, retarded pulp softening and peel de-greening. Pre-treatment with NO also decreased the respiration rate of banana fruit slices during ripening. Delayed pulp softening by NO was associated with decreased activities of PG, EGase, beta-Gal, and total amylase, as well as reduced expression of the MaExp1 gene. Expression of the MaERS2 gene was also suppressed in NO-treated banana fruit slices. Collectively, these findings suggest that NO pre-treament decreased the sensitivity of banana fruit slices to ethylene, and thereby delayed ripening