2,4-epibrassinolide enhance chilling tolerance of loquat fruit by regulating cell wall and membrane fatty acid metabolism

2,4-epibrassinolide (EBR) treatment has the effect of reducing chilling injury (CI) on many kinds of fruits. However, the effect on loquat fruit is unknown. The impacts of 15 μM EBR in response to CI of loquat fruit by regulating cell wall and fatty acid metabolism have been investigated in this study. Our results indicated that EBR treatment notably attenuated the symptom of CI, particularly, inhibited the accumulation of lignin, positively correlated with firmness. In contrast to control fruit, higher levels of water-soluble pectin and chelate-soluble pectin, as well as lower levels of sodium carbonate-soluble pectin, hemicellulose and cellulose were observed in EBR preconditioned fruit. The activities of polygalacturonase (PG), cellulase (Cel) and β-galactosidase (β-gal) were higher in EBR treated-loquat fruit than those in control. The reduction of oleic acid, linoleic acid and linolenic acid were retarded by EBR treatment, which was the consequence of the lower lipoxygenase (LOX) and phospholipase D (PLD) activities. Hence, this work demonstrated that EBR enhanced chilling tolerance in loquat fruit attribute to maintaining the high level of soluble cell wall polysaccharides and unsaturated fatty acids by regulating related-enzymes activities.