Soluble sugars, primarily fructose, glucose, sucrose, and sorbitol, are crucial determinants of fruit flavor and quality. As a core component of biological metabolism, sugar metabolism provides energy and carbon for fruit development, ultimately governing carbohydrate accumulation in mature fruits. This process requires the coordinated activities of multiple enzymes and transporters, modulated by the spatiotemporal expression patterns of their encoding genes. Therefore, it is essential to elucidate both the activities of these enzymes across different fruits and their underlying gene expression patterns. While significant progress has been made in functional genes involved in soluble sugar metabolism and deciphering their regulatory networks, an overall introduction of this knowledge remains lacking. This review presents an integrative analysis of soluble sugar accumulation during fruit development, encompassing spatiotemporal dynamics of key metabolic enzymes, functional characterization of encoding genes, signaling response mechanisms governing gene regulation, and the overarching genetic network.

Soluble sugars are key determinants of fruit quality, directly influencing sensory attributes such as sweetness and flavor, as well as nutritional value and texture. Their content and composition are precisely regulated by sugar-metabolizing enzymes. Key enzymes, including invertase (INV), sucrose phosphate synthase (SPS), sucrose synthase (SUS), fructokinase (FRK), and hexokinase (HXK), play pivotal roles in these processes. However, a systematic and in-depth analysis of their regulatory mechanisms is currently lacking, which hinders a comprehensive understanding of the regulatory network governing fruit sugar metabolism. This review employs bibliometric analysis to systematically examine research trends in fruit sugar metabolism. Furthermore, it synthesizes recent advances in the coordinated regulatory mechanisms from the perspectives of transcriptional regulation, epigenetic modifications, and signal transduction, aiming to provide a clearer framework for future research. At the transcriptional level, transcription factor families such as MYB, WRKY, NAC, and MADS-box achieve precise regulation of sugar metabolism-related genes by specifically binding to the promoters of their target genes. Regarding epigenetic regulation, mechanisms including histone modifications, non-coding RNAs, and DNA methylation influence the expression of sugar-metabolizing enzymes at the post-transcriptional level by modulating chromatin accessibility or mRNA stability. Signaling pathways integrate hormonal signals (e.g., ABA, ethylene), environmental signals (e.g., temperature, light), and sugar-derived signals into the regulatory network, forming complex feedback mechanisms. These regulatory mechanisms not only directly affect sugar accumulation in fruits but also participate in fruit quality formation by modulating processes such as cell turgor pressure and carbon allocation. By integrating recent findings on transcriptional regulation, epigenetics, and signaling pathways, this review provides a theoretical foundation for fruit quality improvement and targeted breeding.

Bananas (Musa spp.) are crucial for food security, but modern cultivars derived from few wild species and propagated vegetatively possess low genetic diversity, and weak disease resistance. Identifying new parental lines is therefore essential for banana breeding. Here we show that Musa cheesmanii exhibits high resistance to Fusarium oxysporum f. sp. cubense tropical race 4. We cross it with two Musa ABB cultivars popular in China, ‘Yulin’ and ‘Jinyu’. The resulting hybrids exhibit enhanced disease resistance, high yield, desirable pulp taste, and extended shelf-life, underscoring the breeding value of this wild species. Additionally, a telomere-to-telomere, gap-free genome of M. cheesmanii is assembled, with multi-omics analyses offering insights into its diversification, black pseudo-stem coloration, and disease resistance. Overall, M. cheesmanii is a promising male parent for enhancing genetic diversity and improving banana cultivars.

Mango fruits are popular for their flavor. Sugar, a key component of fruit nutrition and flavor, determines fruit quality via its composition and content. While many studies explore molecular regulatory pathways of sugar metabolism in various fruits, large-scale physiological screening of related enzymes via advanced mathematical methods is largely neglected, and the physiological mechanism of sugar accumulation in mango remains unclear. This study analyzed glucose, fructose, sucrose and starch contents, and the activities of 11 sugar metabolism-related enzymes (adenosine diphosphate glucose pyrophosphorylase (AGP); sucrose synthase (SS); sucrose phosphate synthase (SPS); protein kinase (PK); starch debranching enzyme (DBE); phosphoglucomutase (PGM); α-amylase; β-amylase; isoamylase (ISA); sucrose invertase (INV); acid invertase (AI)) from fruit growth to post-ripening stages of mango cultivar ‘Renong No.1’, determined the correlations among soluble sugar, starch and enzyme activities, and constructed mathematical models of inter-group relationships using R language. The results showed that glucose, fructose and starch accumulated during fruit growth, while sucrose accumulated during post-ripening. Fructose content was significantly positively correlated with AGP, α-amylase, AI, β-amylase and SPS activities; so was glucose content and AGP activity; sucrose content and AGP, AI, PK, α-amylase, ISA, INV and SPS activities; and sweetness value and AGP, α-amylase, AI, SPS, SS and β-amylase activities. AI, AGP and α-amylase were identified as the key enzymes influencing sweetness value. Ultimately, a new visualizing and digitizing statistical approach for roles of eleven key enzymes in sweet value and soluble sugar component content during mango development was shown.