Alternative Oxidase(AOX) Participated In Regulation Of Cold Resistance And Phenolic Metabolism In Postharvest Sweetpotato Root

China is the largest producer of sweetpotato in the world in terms of planting area and total production.Sweetpotato originates from the tropics and is very sensitive to low temperature and vulnerable to chilling injury,which would deteriorate its eating quality and nutritional values.Previous studies have reported that AOX involved in stress resistance in plants.In this study,we investigated the role of AOX in low-temperature conditioning（LTC）induced cold tolerance and also the potential role of AOX in phenol metabolism in postharvest sweetpotato.After LTC and salicylhydroxamic acid（SHAM）treatment,we analyzed the AOX expression pattern and AOX protein level,respiration,reactive oxygen species,antioxidant system,free proline content,ATP and coenzyme in postharvest sweetpotato during low temperature storage.Results showed that the expression of Ib AOX1a and Ib AOX1b increased rapidly,while the transcript level of Ib AOX2remain relatively stable.LTC reduced root CI index,suppressed relative electrolyte leakage,malondialdehyde content,the rate of O₂^·-production and H₂O₂content,improved antioxidant enzyme（SOD,CAT,APX,GR）activities,free proline content,reduced glutathione and adenosine triphosphate contents,reduced coenzyme contents.However,SHAM treatment reversed the above-mentioned positive effects of LTC treatment.Therefore,the results of this study confirmed that AOX participates in the LTC induced chilling resistance in sweetpotato roots.We further studied the role of AOX in phenolic metabolism of postharvest sweet potato roots under low temperature storage by measuring free phenolic acid content,total phenol content,antioxidant ability by DPPH.The results showed that low temperature induced AOX gene expression and protein accumulation,inhibited respiratory rate,increased free phenolic acid content,total phenol content,antioxidant ability.However,SHAM treatment reduced the above-mentioned trends of the above parameters.Therefore,AOX participates in the regulation of phenol metabolism during the low temperature storage of sweetpotato roots.