Abstract
The role of melatonin in the regulation of fruit ripening and the mechanism involved remain largely unknown. In “Moldova” grape berries, melatonin accumulated rapidly from onset of veraison, reached the maximum at 94 days after bloom (DAB) and then exhibited low levels at late stages of berry ripening. By contrast, abscisic acid (ABA) and hydrogen peroxide (H2O2) exhibited different accumulation patterns, and ethylene was primarily produced immediately before veraison. Further experiments demonstrated that 10 and particularly 100 µM melatonin treatments increased the levels of ABA, H2O2, and ethylene production and promoted berry ripening compared with the control treatment, whereas 0.1 and 1.0 µM melatonin did not lead to clear effects. Additionally, the application of inhibitors indicated that ABA, H2O2, and ethylene participated in the regulation of berry ripening induced by melatonin, and the suppression of ethylene biosynthesis produced the greatest inhibitory effects on melatonin-induced berry ripening compared with those of ABA and H2O2. Melatonin also promoted ethylene production via ABA. In summary, 10 and particularly 100 µM melatonin treatments promoted berry ripening, which was accomplished, at least partially, via the other signaling molecules of ABA, H2O2, and particularly ethylene. This research provides insight into melatonin signaling during berry ripening and may advance the application of melatonin to accelerate berry ripening.
Highlights
Grapevine is one of the most important fruit crops and is planted worldwide
In 2016, titratable acid continued to decrease and total soluble solids (TSS) continued to increase from 60 days after bloom (DAB), anthocyanin began to accumulate at 78 DAB, and coloring began at 94 DAB (Fig. 1a)
Melatonin and abscisic acid (ABA) prominently accumulated at veraison, and thereafter, melatonin sharply declined, ABA remained at relatively high levels; the large accumulation of H2O2 was late compared with that of melatonin and ABA during berry ripening
Summary
Grapevine is one of the most important fruit crops and is planted worldwide. The high economic and nutritional value of grapevine has encouraged many researchers to study the physiological and molecular basis of berry development and berry quality formation. Grapes are classified as non-climacteric fleshy fruits and might be considered a model species to study the ripening of non-climacteric species[2]. Based on the substantial accumulation during fruit maturation in nonclimacteric fruits, abscisic acid (ABA) plays an important role in accelerating fruit ripening, and based on RNA-Seq analysis, is a primary regulator of grape berry ripening onset[5,6]. One of the best-known roles of ABA is the ability to upregulate anthocyanin production of grape berries[7]. A few recent studies show that grape berry tissues have a fully functional pathway for ethylene biosynthesis that is activated immediately before veraison; ethylene perception is critical for some grape berry ripening[8,9].
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