Synergistic Changes in Ascorbic Acid and Soluble Sugar Contents in Apricot Fruits and the Related Regulatory Mechanisms

Soluble sugars, including sucrose, are vital to the overall quality of apricot fruits, influencing attributes such as sweetness, flavor, and texture. As the primary soluble sugar, sucrose plays a central role in determining fruit quality. The synthesis and accumulation of sucrose, as well as its interaction with ascorbic acid metabolism, are regulated by various enzymes, including sucrose synthase and invertase. While several genes related to sucrose metabolism have been identified in apricots, the mechanisms by which sucrose and ascorbic acid work together to regulate fruit quality remain "is not fully elucidated". In the present investigation, the changes in soluble sugar and ascorbic acid levels throughout fruit development were examined, and the mechanisms underlying the changes in soluble sugar and ascorbic acid levels were examined in 'Wuyuexian' apricots (WYX) and 'Lanzhoudajie' apricots (LZ). The data revealed that the sucrose content of 'WYX' was significantly higher than that of 'LZ', whereas the sorbitol levels of 'LZ' were higher than 'WYX'. The fructose contents of both varieties increased later in growth, and the ascorbic acid content of 'LZ' was three times higher than that of 'WYX' during the early stage of fruit growth. These trends became intensified in both varieties after the rapid growth stage, with 'WYX' having the highest sucrose content. Additionally, transcriptomic analysis, K-means analysis, and weighted correlation network analysis (WGCNA) howed the expression levels of genes related to sucrose and ascorbic acid metabolism, the synergistic effects of gene clusters, and the complex associations among genes. Moreover, the key hub genes <i>HSFB1</i> and <i>FTIP4</i> were identified, which play crucial roles in regulating sucrose and ascorbic acid metabolis. However, transcriptome analysis of gene expression only partially reflects metabolism regulation, and further in-depth investigations are required to elucidate other regulatory mechanisms. Our research revealed a relationship between the synthesis of ascorbic acid and soluble sugars in apricots and offers new perspectives on molecular breeding and germplasm development in apricots and establishment of germplasm resources.