Effect Of Temperature Pretreatment On Postharvest Chilling Injury And The Expression Of Cbf Transcription Factor In ‘hongyang’ Kiwifruit

Kiwifruit is cold-sensitive and very susceptible to chilling injury during low-temperaturestorage. C-repeat/dehydration-responsive element binding factors (CBFs) are key regulatorsin cold-response. In this study, kiwifruit (Actinidia chinensis cv. Hongyang) were used asmaterial and a637bp CBF gene was identified from it by RT-PCR and RACE. The effect ofthree different prestorage hot water treatments (35℃,45℃,55℃) and low temperatureconditioning (5℃3d) on chilling injury tolerance and expression of the transcription factorCBF in ‘Hongyang’ kiwifruit was investigated. The results are as follows.1. Using the total RNA from cold-treated ‘Hongyang’ kiwifruit as the template, a partialCBF gene fragment (637bp) was isolated and deposited in GenBank under AccessionNumber KF672602. The sequence analysis of the deduced amino acid sequence of AcCBFrevealed that AcCBF contained a highly conserved AP2/EREBP DNA-binding domainflanked by KK/RPAGRxKFxETRHP and DSVWR signature sequences. The fourteenth (Val)and the nineteenth (Glu) amino acid residues were predicted to be the key residues for theDRE element binding. A BLASTp search revealed that the deduced amino acid sequence ofAcCBF shared high identities with other CBF/DREB sequences.2. Both35℃and45℃treatment can significantly reduced chilling injury index andchilling injury incidence, inhibited the accumulation of malonaldehyde and the increase inmembrane permeability and decreased respiratory and ethylene production rate. Moreover,these two treatments, maintained higher peroxidase (POD) activity and lower polyphenoloxidase (PPO) and lipoxygenase (LOX) activity. AcCBF expression level was higher in35℃and45℃treatment. These two treatments also had better commercial qualities at the end ofstorage.55℃treatment increased symptoms of chilling injury in ‘Hongyang’ kiwifruit andresulted in opposite physiological effects in comparison with35℃treatment and45℃treatment. It is suggested that dipping in45℃hot water for10min was the most effective atreducing chilling injury of ‘Hongyang’ kiwifruit.3. Low temperature conditioning (LTC) treatment was effective at enhancing chillingtolerance of ‘Hongyang’ kiwifruit, as fruit in LTC treatment exhibited lower chilling injuryindex and incidence, membrane permeability, malonaldehyde content, lipoxygenase (LOX) and polyphenol oxidase (PPO) activity. At the end of storage, fruit in LTC treatmentmaintained higher accepted fruit percentage. Moreover, in accordance with the effect of LTCtreatment on physiological parameters of chilling injury, CBF transcription factor expressionlevel was higher in the LTC treatment. These results indicate that LTC treatment is effectivefor alleviating symptoms of chilling injury in ‘Hongyang’ kiwifruit during low-temperaturestorage, but not better than45℃treatment.