Deciphering serotonin's functional role in postharvest: Fruit-specific preservation of red fruit quality

Serotonin is a widely conserved signaling molecule essential for plant development and stress responses, but its role in fruit postharvest physiology remains largely unexplored. This study aimed to evaluate the effects of 100 μM exogenous serotonin on delaying deterioration and preserving fruit quality in highly perishable fruits, including strawberries, blueberries, raspberries, and sweet cherries, stored at room temperature. Results showed that serotonin reduced decay incidence and severity in strawberries and blueberries by 40% at half-storage. In strawberries, serotonin also contributed to maintaining fruit color, while in blueberries it notably reduced weight loss. This delay in postharvest deterioration was associated with elevated endogenous serotonin levels and fruit-specific modulation of stress-related hormones, increasing jasmonic acid and salicylic acid in strawberries and blueberries, respectively, rather than melatonin, its downstream metabolite. By contrast, exogenous serotonin had a more limited effect on the other fruits. In raspberries, serotonin had a smaller effect on decay but still improved fruit quality by enhancing anthocyanin content, whereas in sweet cherries it did not reduce decay or improve quality parameters, and hormonal balance remained largely unchanged in both fruits. Altogether, these findings provide the first evidence that serotonin can act as a selective modulator of postharvest responses in berries, highlighting its potential for targeted, fruit-specific strategies to improve shelf life and quality.