Molecular responses of citrus fruit to anaerobic stress

The molecular responses of plants to anaerobic stress have been extensively studied in roots during and after flooding; far less has been done with ripening fruits, and very little is known about the behavior of citrus fruit during postharvest storage under restricted O₂ availability conditions. Using 'Star Ruby' grapefruit and 'Murcott' mandarin as plant materials and N₂ atmosphere treatment as the major experimental system, we studied the molecular responses of citrus fruits to anaerobiosis. The major response of citrus fruit to anaerobiosis is a metabolic shift towards ethanol fermentation, and the regulation of ethanol fermentation takes place at both transcriptional and posttranscriptional levels. Ethylene is not a major player in the responses to anaerobiosis. 'Murcott' mandarin is more sensitive than 'Star Ruby' grapefruit to anaerobiosis, peel (flavedo) and juice vesicles respond differently to anaerobiosis. Taken together, our data reveal both general and citrus fruit-specific anaerobic-response mechanisms.