Carbohydrate and fatty acid metabolisms are involved in delaying senescence of ‘Zaosu’ pear fruit following caffeic acid treatment

Abstract

‘Zaosu’ pears, being an early-maturing variety, are susceptible to senescence and quality decline, resulting in significant economic losses during postharvest storage. Caffeic acid not only possesses antioxidant and antimicrobial properties but also exhibits a preservative effect on fruit and vegetables. This study was conducted to explore the possible mechanisms of delaying ‘Zaosu’ pear fruit senescence by caffeic acid immersion. Results indicated that caffeic acid restrained respiratory rate and ethylene release in pears. Moreover, caffeic acid enhanced amylase and sucrose synthase-synthesis activities, sucrose synthase expression, as well as gene expression and enzymatic activity of sucrose phosphate synthase. This occurred concurrently with the suppression of sucrose synthase-cleavage, sorbitol oxidase, nicotinamide adenine dinucleotide-sorbitol dehydrogenase, and nicotinamide adenine dinucleotide phosphate-sorbitol dehydrogenase activities, as well as the down-regulation of fructokinase, hexokinase, and sorbitol dehydrogenase expressions. Additionally, the enzymatic activities and gene expressions of neutral invertase and acid invertase were inhibited in ‘Zaosu’ pears by caffeic acid. The variations observed in these parameters led to an improvement in reducing sugar and soluble sugar contents in pears. Furthermore, caffeic acid reduced palmitic acid content, concurrently increasing linoleic acid and oleic acid levels. This phenomenon was contributed to the enhancement of gene expressions, including ∆9-stearyl-ACP desaturase, ketoacyl-ACP reductase, ∆12-fatty acid desaturase 3, enoyl-CoA reductase, β-ketoacyl-CoA synthase, acyl carrier protein, long-chain acyl-CoA synthetase, fatty acid synthase, and acetyl-CoA carboxylase, the reduction of phospholipase D expression, and the improvement of fatty acid synthase activity. The treatment also suppressed lipoxygenase activity and gene expression in ‘Zaosu’ pears. Taken together, caffeic acid effectively postpones ‘Zaosu’ pear fruit senescence via modulating carbohydrate and fatty acid metabolisms.