International Journal of Horticulture, 2025, Vol.15, No.5, 234-241 http://hortherbpublisher.com/index.php/ijh 237 example, transcription factors like MYB and WRKY have been shown to be accountable for the regulation of genes related to antioxidant metabolism. These regulatory mechanisms ensure that antioxidant defense systems are able to adaptively modulate depending on the constantly fluctuating oxidative environment during fruit ripening (Durán-Soria et al., 2020). 5 Coordinated Regulation of Softening, Sugar Accumulation, and Antioxidant Metabolism 5.1 Influence of ethylene signaling on sugar metabolism Ethylene plays a major role in sugar metabolism control during fruit ripening. Ethylene is a key hormone signal for controlling the sugar composition and softening potential of the fruit. Ethylene interacts synergistically with abscisic acid (ABA) in controlling major changes in fruit development, including sugar accumulation and cell wall rupture, both of which are integral to fruit ripening. The ethylene and sugar cross-talk is complex, with numerous transcription factors and metabolic genes participating to collectively regulate sugar content fluctuations in fruits (Li et al., 2017). 5.2 Interaction between cell wall degradation and sugar transport During fruit ripening, cell wall breakdown is directly related to sugar transport and accumulation. During the maturation process, the enzymes such as convertases and sucrose synthase are mainly involved in the breakdown of complex carbohydrates to glucose and fructose, which are transported and accumulated inside the fruit. It has been found using research that transcription factors such as HpDof1.7 and HpDof5.4 can enhance the level of expression of genes associated with sugar metabolism and improve the accumulation of soluble sugars within Pitayas (Peng et al., 2022; Da Graca Tomas et al., 2023). Cell wall breakdown and the transport of sugar work together to contribute significantly to the formation of fruit texture and flavor (Figure 1). Figure 1 Cell walls undergo metabolic responses associated with softening during fruit ripening (Adopted from Peng et al., 2022) 5.3 Regulation of fruit softening and sugar accumulation by antioxidant metabolism Antioxidant metabolism is essential in regulating fruit softening and sugar loading. Antioxidants (such as ascorbic acid) regulate the mechanism of fruit ripening by modulating oxidative stress and maintaining cellular integrity. Balancing antioxidant and sugar metabolism is essential to achieve optimal fruit quality because it controls the
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