Inhibition of ethylene biosynthesis by antisense ACC oxidase RNA prevents chilling injury in Charentais cantaloupe melons

Non-freezing low temperature storage causes injury to melons and most other fruit and vegetables of tropical and subtropical origin, We demonstrate he re that ethylene suppression through an antisense ACC oxidase (ACO) gene co nsiderably reduced the sensitivity of Charentais cantaloupe melons to chill ing injury. In contrast to wildtype fruit, antisense ACO melons did not dev elop the characteristic chilling injury of pitting and browning of the rind neither when stored at low temperature (3 weeks at 2 degrees C) nor upon r ewarming, Treating antisense melons with 19 p.p.m. ethylene for more than i d prior to cold storage resulted in the restoration of chilling sensitivity . When the ethylene treatment was performed after cold storage, the chillin g injury symptoms did not appear. The tolerance to chilling was associated, vith a lower accumulation of ethanol and acetaldehyde, reduced membrane det erioration and higher capacity of the fruit to remove active oxygen species . The activities of catalase, superoxide dismutase and peroxidase were mark edly increased in antisense ACO fruit in comparison with wild-type fruit, p articularly upon rewarming and post-storage ethylene treatment. Severe chil ling injury symptoms were correlated with a lower activity of activated oxy gen scavenging enzymes. These results demonstrate that ethylene acts in con junction with low temperature to induce metabolic shifts that participate i n the development of chilling injury.