Changes in enzymatic activity, accumulation of proteins and softening of persimmon (Diospyros kaki Thunb.) flesh as a function of pre-cooling acclimatization

Abstract

a b s t r a c tOne of the major causes of 'Fuyu' persimmon loss after cold storage (CS) is the breakdown of its flesh, which results in the production of a translucent fruit (a water-soaked fruit). It is believed that the cause of this disturbance is linked to disorganization of the cytoskelet and endomembrane system, which changes the synthesis and transport of proteins and metabolites, resulting in incomplete ripening. To test this hypothesis, 'Fuyu' persimmon was subjected to three different postharvest treatments (T): Controlharvested and kept at 23 ± 3 • C and relative humidity (RH) of 85 ± 5% (room temperature, RT) for 12 days, T1 -harvested and kept under cold storage (CS) (1 ± 1 • C and RH of 85 ± 5%) for 30 days followed by RT storage for 2 days, T2 -kept under RT for 2 days (acclimatization) followed by CS for 30 days. Control and T2 resulted in fruit with decreased flesh firmness (FF), and increased soluble solids (SS) and ascorbic acid (AA) contents. In these fruit the activity of endo-1,4-ß-glucanase (endo-1,4-ß-gluc), pectin methylesterase (PME), polygalacturonase (PG) and ß-galactosidase (ß-gal) increased. T1 resulted in translucent fruit with decreased FF, without any enzymatic activity changes, probably due to the physical disruption of the cytoskeleton. Further, there was an increased content of proteins corresponding to expansins in fruit kept under Control and T2 conditions, which suggests that these conditions do contribute to the synthesis and/or transport of proteins involved in the process of solubilization of the cell wall. In these fruit, there was also a major accumulation of gene transcripts corresponding to heat shock proteins (HSPs) of organelles related to endomembrane, which suggests participation of these genes in the prevention of damage caused by cold conditions. These data proved the hypotheses that acclimatization contributes to the expression of HSPs, and synthesis and transportat of proteins involved in the solubilization of the cell wall. The expression of these genes results in the normal ripening of the persimmon, as confirmed by the evolution of ethylene production.

Harvest and Postharvest Quality of Persimmon Fruit:physicochemical and Nutritional Aspects.

“…Thus the ethylene production observed in the 36-hour-treated fruits probably contributes to the softening associated with normal fruit ripening. This is in accordance with Souza, Souza, Tiecher, Girardi, Nora, Silva, Argenta and Rombaldi (2011), who associated flesh gelling alleviation in 'Fuyu' by a prestorage acclimatisation treatment with the higher ethylene production of acclimatised fruits when compared to untreated ones which manifested flesh gelling symptoms. These authors also associated treated fruit softening with ethylene production and subsequent changes in the activity of endo-1,4-B-gluc, PME, PG and B-gal enzymes, while no activation of these enzymes was detected in the fruits manifesting flesh gelling; thus these authors attributed the breakdown of chilling-injured fruit to a physical disruption of the cytoskeleton due to low temperature exposure.…”

“…Members of the PG, XTH and EXP gene families have been shown to be involved in fruit softening processes of persimmons (Nakatsuka et al, 2011;De Souza et al, 2011;Zhu et al, 2013). Fig.…”

“…Zhang et al 2012 reported that the expression of DkEXP3 in 'Fupingjianshi' persimmon was inhibited by exogenous gibberellic acid, a plant growth regulating hormone, which can result in delayed ripening. PG enzymes are known to be necessary for cell division; their activities are known to increase during ripening of fruit, and each enzyme isoform makes a specific contribution to this process (De Souza et al, 2011). The relative expression of DkPG1 (Fig.…”

“…Thus Luo and Xi (2005) reported in chilling injured fruit that the primary cell wall and the middle lamella cannot be dissolved normally, while De Souza et al (2011) reported an increase in the activity of cell wall-degrading enzymes such as endo-1,4-β-glucanase, pectin methylesterase, polygalacturonase and β-galactosidase. In 'Rojo Brillante' persimmon, microstructural studies have shown that 1-MCP preserves the integrity of cell walls and adhesion between adjacent cells .…”

“…In 'Rojo Brillante' persimmon, microstructural studies have shown that 1-MCP preserves the integrity of cell walls and adhesion between adjacent cells . Moreover the loss of the cell walls integrity and the flesh breakdown associated with CI development has been linked to increased levels of ethylene (De Souza et al, 2011;Luo and Xi, 2005;Orihuel-Iranzo et al, 2010;. According to Orihuel-Iranzo et al (2010), the increase in ethylene production upon transfer from chilling to nonchilling temperature is part of the fruit chilling response since it does not occur at nonchilling temperatures, and it also appears to be responsible for the collapse of the fruit.…”