Hydrogen Sulfide Maintained the Good Appearance and Nutrition in Post-harvest Tomato Fruits by Antagonizing the Effect of Ethylene

Abstract

Hydrogen sulfide (H₂S) could act as a versatile signaling molecule in delaying fruit ripening and senescence. Ethylene (C₂H₄) also plays a key role in climacteric fruit ripening, but little attention has been given to its interaction with H₂S in modulating fruit ripening and senescence. To study the role of H₂S treatment on the fruit quality and nutrient metabolism, tomato fruits at white mature stage were treated with ethylene and ethylene plus H₂S. By comparing to C₂H₄ treatment, we found that additional H₂S significantly delayed the color change of tomato fruit, and maintained higher chlorophyll and lower flavonoids during storage. Moreover, H₂S could inhibit the activity of protease, maintained higher levels of nutritional-related metabolites, such as anthocyanin, starch, soluble protein, ascorbic acid by comparing to C₂H₄ treatment. Gene expression analysis showed that additional H₂S attenuated the expression of beta-amylase encoding gene BAM3, UDP-glycosyltransferase encoding genes, ethylene-responsive transcription factor ERF003 and DOF22. Furthermore, principal component analysis suggested that starch, titratable acids, and ascorbic acid were important factors for affecting the tomato storage quality, and the correlation analysis further showed that H₂S affected pigments metabolism and the transformation of macromolecular to small molecular metabolites. These results showed that additional H₂S could maintain the better appearance and nutritional quality than C₂H₄ treatment alone, and prolong the storage period of post-harvest tomato fruits.

Keywords: ethylene; hydrogen sulfide; nutritional quality; post-harvest ripening; tomato fruits.

FIGURE 1

The phenotypic change of post-harvest tomato fruits with C₂H₄ or C₂H₄-H₂S treatment. (A) The phenotypic change of post-harvest tomato fruits. (B) The color parameter a*/b* value changes with C₂H₄ or C₂H₄-H₂S treatment during tomato post-harvest storage. a* value represents a range from magenta to green, and b* value represents a range from yellow to blue. Values are the means ± SD (n = 3). The experiments and following ones were carried out at room temperature and 85-90% relative humidity. The symbols * and ** stand for significant difference between C₂H₄ and C₂H₄-H₂S at p < 0.05 and p < 0.01, respectively.

FIGURE 2

Effects of C₂H₄ and C₂H₄-H₂S on the contents of total chlorophyll (A), chlorophyll a (B), chlorophyll b (C) in post-harvest tomato. Data are presented as means ± SD (n = 3). * and ** in this figure and following ones stand for a significant difference between C₂H₄ treatment and C₂H₄-H₂S co-treatment at p < 0.05 and p < 0.01, respectively.

FIGURE 3

Effect of C₂H₄ and C₂H₄-H₂S on the contents of anthocyanin (A), flavonoids (B), carotenoid (C), total phenols (D). Data are presented as means ± SD (n = 3). The symbols * and ** stand for significant difference between C₂H₄ and C₂H₄-H₂S at p < 0.05 and p < 0.01, respectively.

FIGURE 4

Effect of C₂H₄ and C₂H₄-H₂S on activity of amylase (A), protease activity (B), content of starch (C) and content of soluble protein (D). Data are presented as means ± SD (n = 3). The symbols * and ** stand for significant difference between C₂H₄ and C₂H₄-H₂S at p < 0.05 and p < 0.01, respectively.

FIGURE 5

Changes of contents of reducing sugar (A), titratable acid (B), the ratio of sugar to acid (C) and ascorbic acid (D) in C₂H₄ treatment and C₂H₄-H₂S co-treatment. Data are presented as means ± SD (n = 3). The symbols * and ** stand for significant difference between C₂H₄ and C₂H₄-H₂S at p < 0.05 and p < 0.01, respectively.

FIGURE 6

Changes in the gene expression of beta-amylase encoding gene BAM3 (A), UFGT73 (B), UFGT5 (C), ethylene response factor ERF003 (D), DOF22 (E), WRKY51 (F) in tomato fruit during storage after C₂H₄ and C₂H₄ + H₂S treatment for 1 day. Error bars indicate standard error (n = 3). Asterisks indicate significant differences between C₂H₄ (ETH) and C₂H₄ + H₂S (E-H) co-treated fruit according to the Student’s t-test (*p < 0.05, **p < 0.01).

FIGURE 7

Principal component analysis the main metabolites of post-harvest tomato fruits. PC1∼PC3 were respectively represented the contribution rate of principal components. C₂H₄ treatment groups were marked as “co” and square, C₂H₄-H₂S treatment groups were marked by triangle. Metabolites are expressed by A∼N. (A) Protease activity, (B) Soluble protein, (C) Activity of amylase, (D) Starch content, (E) Reducing sugar, (F) Chlorophyll a, (G) Chlorophyll b, (H) Chlorophyll, (I) flavonoid, (J) anthocyanins, (K) Carotenoids, (L) Total phenol, (M) Titratable acid, (N) Ascorbic acid. Data represent the normalized mean values of three independent biological replicates.

FIGURE 8

Correlation analysis (A) and the heatmap (B) among the parameters of bioactive compounds. (A) The correlation analysis the relationship among bioactive compounds. Correlation coefficient was analyzed using R scripts. (B) The heatmap analyzed the change of bioactive compounds in the storage periods of tomato fruit. co- indicated control group (C₂H₄), co-treatment group no marked. (A) Protease activity, (B) Soluble protein, (C) Activity of amylase, (D) Starch content, (E) Reducing sugar, (F) Chlorophyll a, (G) Chlorophyll b, (H) Chlorophyll, (I) flavonoid, (J) anthocyanins, (K) Carotenoids, (L) Total phenol, (M) Titratable acid, (N) Ascorbic acid.