Search

Membrane deterioration is an inherent aspect of the advancement in senescence and loss in fruit quality during storage. Postharvest technologies used for extending shelf life and quality are targeted to reduce membrane damage through downregulating or blocking ethylene action. In this study, mature green tomato fruit were treated with inhibitors of ethylene receptor (ETR), phosphatidylinositol 3-kinase (PI3K) and phospholipase D (PLD), all recognized to be targets of regulation of fruit ripening. The inhibitors used included 1-methylcyclopropene (1-MCP, an ethylene receptor blocker), wortmannin (an inhibitor of PI3K), and hexanal (a PLD inhibitor). Fruit were treated at optimal levels of the inhibitors and were stored at 21 °C for 10 days. Color development was strongly delayed in wortmannin treated tomatoes just as in 1-MCP treated fruit; while, changes in respiration, firmness and ethylene evolution were very similar to that of control fruit. Hexanal delayed the initiation of these changes; while 1-MCP and wortmannin blocked the ripening process. Changes in expression levels of key genes involved in ethylene signalling, phosphoinositide metabolism, and lycopene synthesis that occurred in response to inhibitors, suggested potential roles for PI3K and PLD in ethylene signalling. Furthermore, fruit treated with all the three inhibitors showed a marked reduction in PLD transcript levels; suggesting that, regulation of PLD gene expression is a common critical regulatory point that regulates ripening. Lowered PLD levels may reduce membrane lipid catabolism and the generation of phosphatidic acid (PA), an intermediate in ethylene signalling regulation through downstream components. [ABSTRACT FROM AUTHOR]

Aqueous compositions of hexanal, an inhibitor of phospholipase D, has been shown to enhance the shelf life and quality of fruits and vegetables. In the present study, sweet bell pepper fruit were exposed to hexanal vapor and its effect on quality attributes, shelf-life, and antioxidant enzyme activities were evaluated during storage at 7 day intervals for 21 d. Peppers subjected to hexanal vapor treatments (0.005, 0.01, and 0.02%, w/w) showed a significant (p < 0.05) delay in ripening process and preservation of postharvest qualities than untreated peppers, even at 21 d of storage. Treated fruit were characterized by increased firmness, a reduction in physiological water loss and lower electrical conductivity than control fruit, which indicated better membrane preservation. These treatments also resulted in an increase in the levels of antioxidant enzyme activities, specifically that of superoxide dismutase, catalase, glutathione reductase and guaiacol peroxidase. Evidences from the present study indicate that postharvest hexanal vapor treatment at optimal levels can effectively enhance the quality and shelf life of sweet bell peppers. [ABSTRACT FROM AUTHOR]

• Hexanal exposure for a minimum of 6 h was essential to delay pepper fruit ripening. • Head space hexanal concentration decreased in the presence of pepper fruit. • Volatile emission was higher in hexanal treated fruit. • Hexanal repressed carotenoid biosynthesis gene expression in pepper. • Phospholipase Dα expression was lnhibited in hexanal treated fruit. Phospholipase D (PLD) is a key enzyme involved in membrane lipid catabolism. Hexanal, a C6 volatile aldehyde is a strong PLD -inhibitor, and has been observed to enhance the shelf life and quality of horticultural produce. In the present study, the effect of hexanal vapor exposure on the postharvest quality and ripening response of bell pepper fruit was evaluated. Hexanal exposure for a minimum of 6 h was found to be essential to delay ripening in bell pepper fruit. Quantification of head space hexanal levels in the presence of pepper fruit revealed a gradual decrease in concentration, while it remained relatively steady close to the peak value in the absence of pepper fruit. Hexanal treated bell peppers subjected to 21 d of postharvest storage evolved higher levels of aroma volatiles than untreated peppers. Hexanal vapor treatment induced significant alterations in the transcript accumulation and expression of genes involved in the carotenoid biosynthetic pathway, antioxidant enzyme systems, and the LOX pathway in stored pepper fruit. Real time PCR analysis also confirmed the near-complete downregulation of expression of genes encoding PLD α, β, δ and ζ isoforms in hexanal vapor treated peppers. The results suggest that hexanal vapor treatment can beneficially influence the expression of genes in multiple biochemical pathways, which could ultimately result in enhancing the shelf life and quality of horticultural produce. [ABSTRACT FROM AUTHOR]