# Transcriptional Regulatory Networks Oscillate Seasonal Plasticity of Fruit Metabolism in Melon
## 4 Discussion
The protein-protein interactions of many proteins with HSP70s have been identified. These combinations of interactions provide opportunities to study the role and molecular strategies of HSP70s. External fruit color is a signal of ripeness and nutritional quality [53]. Carotenoid is one of the major pigments accumulated in the melon [54], and temperature stimulus can alter carotenoid accumulation in melon fruit. It has been reported that the degradation rate and folding state of phytoene synthase (PSY) are modulated by HSP70s, which affects carotenoid accumulation in ripe tomato fruit [55]. The HSP70s and interacting proteins identified in this study suggest that HSP70s are associated with the transcriptional regulatory network of fruit in response to signals from seasonal conditions. Understanding how plants respond to environmental signals from seasonal conditions is an important step in developing fruit crops with broad adaptability. Under seasonal growing conditions, light, like day length, is another important signal that influences growth and development. In the light-mediated signaling pathway, Constitutively Photomorphogenic 1 (COP1) is a master regulator that is involved in diverse biological processes in plants and animals, including development and metabolism, and responses to abiotic and biotic stimuli [56]. Recent studies have shown that SmCOP1 functions to inhibit tomato fruit ripening, reduce carotenoid content, and decrease ethylene production in fruits [57]. In addition, OsCOP1 has been reported to play a critical role in flavonoid biosynthesis in rice seeds [58], and Arabidopsis [59; 60]. We found that COP1 is also involved in the transcriptional regulatory network in response to signals from seasonal conditions, suggesting that it could be used as a target for genetic improvement for resilience in response to environmental cues. Although there is no direct evidence to show that components of photosynthesis, such as Rubisco activase (RCA) and NADP-glyceraldehyde-3-phosphate dehydrogenase (GAPA/GAPB), are associated with metabolism in fruits, it is undoubtedly clear that carbohydrate fixation can increase the metabolic potential [61]. Furthermore, cyanobacterial RCA has a dual function in metabolic repair and recruitment to carboxysomes [62]. In addition, as a molecular chaperone in the regulation of Rubisco, RCA is essential for photosynthesis and is also sensitive to moderate heat stress, suggesting a possible role in response to environmental signaling stimulus [63; 64]. Genetic manipulation of RCA clearly affects thermal tolerance in rice [65] and abiotic stress responses (drought, salinity, and heat) responses in Arabidopsis [66]. The association of RCA with the fruit transcriptional regulatory network in response to seasonal conditions signals suggests its possible role in source-sink regulation of metabolite accumulation in fruit. In crops grown under seasonal conditions, fluctuations in environmental factors such as temperature and photoperiod introduce variability in growth, yield, and quality. Therefore, it is essential to thoroughly dissect the regulatory network of important environmental factors affecting crop metabolism, growth, and development. However, the precise mechanism connecting the regulation of metabolites with seasonally mediated signals is present almost as a blind box. The direct interactions between key seasonal signaling components and metabolic regulators remain largely unclear, hampering further understanding of how seasonal signals incrementally affect the metabolic network stepwise. The identification of hub genes and pathways in response to seasonal growing conditions during fruit development in melon provides new insights and comprehensive information for studying the relationship between seasonal changes and metabolic dynamics.