Exogenous glutathione maintains the postharvest quality of mango fruit by modulating the ascorbate-glutathione cycle

Abstract

Background: Mango fruit is prone to decay after harvest and premature senescence, which significantly lowers its quality and commercial value.

Methods: The mango fruit (Mangifera indica L.cv. Guixiang) was treated with 0 (control), 2, 5, and 8 mM of reduced glutathione (GSH) after harvest. The fruit was stored at 25 ± 1 °C for 12 days to observe the changes in the antioxidant capacity and postharvest quality.

Results: Compared with the control, the 5 mM GSH treatment significantly decreased the weight loss by 44.0% and 24.4%, total soluble solids content by 25.1% and 4.5%, and soluble sugar content by 19.0% and 27.0%. Conversely, the 5 mM GSH treatment increased the firmness by 25.9% and 30.7% on days 4 and 8, respectively, and the titratable acidity content by 115.1% on day 8. Additionally, the 5 mM GSH treatment decreased the malondialdehyde and hydrogen peroxide contents and improved the antioxidant capacity of mango fruit by increasing the superoxide dismutase and peroxidase activities and upregulating the expression of the encoding genes. Meanwhile, the higher levels of monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase enzyme activities and gene expressions accelerated the AsA-GSH cycle, thereby increasing the accumulation of AsA and GSH and maintaining the redox balance.

Conclusions: Overall, the experimental results suggest that 5 mM GSH maintains high antioxidant capacity and postharvest quality of mangoes and can use as an effective preservation technique for postharvest mangoes.

Keywords: Antioxidant; Fruit quality; Glutathione; Mango; Reactive oxygen species.

Figure 1. The phenotype in mango fruit under exogenous GSH during storage.

Disease spot color is black in mango fruit.

Figure 2. Changes in weight loss (A) and firmness (B) in mango fruit under exogenous GSH during storage.

The error bars represent the standard error (n = 4). Bars with a different letter within a sampling date are significantly different (P < 0.05).

Figure 3. Changes in pH (A), total soluble solids (TSS) (B), titratable acidity (TA) (C), and soluble sugar (D) in mango fruit under exogenous GSH during storage.

The error bars represent the standard error (n = 4). Values with a different letter within a sampling date are significantly different (P < 0.05).

Figure 4. Changes in MDA content in mango fruit under exogenous GSH during storage.

The error bars represent the standard error (n = 4). Bars with a different letter within a sampling date are significantly different (P < 0.05).

Figure 5. Changes in H₂O₂ content in mango fruit under exogenous GSH during storage.

The error bars represent the standard error (n = 4). Bars with a different letter within a sampling date are significantly different (P < 0.05).

Figure 6. Changes in redox status in mango fruit under exogenous GSH during storage.

The error bars represent the standard error (n = 4). Bars with a different letter within a sampling date are significantly different (P < 0.05).

Figure 7. Changes in activities and gene expression levels of SOD (A and B), POD (C and D), CAT (E and F) in mango fruit under exogenous GSH during storage.

The error bars represent the standard error (n = 4). Bars with a different letter within a sampling date are significantly different (P < 0.05).

Figure 8. Changes in activities and gene expression levels of APX (A and B), MDHAR (C and D), DHAR (E and F) and GR (G and H) in mango fruit under exogenous GSH during storage.

The error bars represent the standard error (n = 4). Bars with a different letter within a sampling date are significantly different (P < 0.05).

Figure 9. Putative mechanism of exogenous GSH on antioxidant capacity in postharvest mango fruit.