Regulatory insight into the metabolic changes of sugars and organic acids during strawberry ripening: Roles of phytohormones, genes and transcription factors

The composition and ratio of sugars and organic acids are crucial for strawberry ( Fragaria × ananassa Duch) taste and flavor. Strawberry at five development and ripening stages-small green (SG), big green (BG), white (W), pink (P) and red stage (R) were analyzed for phytohormones, sugars, organic acids, related genes and transcription factors (TFs) expressions dynamics. The signals of auxin (IAA), salicylic acid (SA), brassinolide (BR), 24-epibrassinolide (EBL), gibberellin (GA) 3, GA 5 , GA 14 and GA 19 increased at the development stage, while the relative abundance of abscisic acid (ABA), melatonin (MT) and GA 51 was higher at the ripening stage. Sucrose and glucose were the primary sugars, and malic acid exhibited the highest content. The expression levels of FaSPS , FaSS , FaMDH, FaTCP7 , FaNAC73 , FaARF2 and FaCMB1 decreased, while the FaCS expression level increased during ripening. Correlation network analysis revealed trends of association between sugars/organic acids accumulation and specific phytohormones and gene expression level. This study significantly deepens the understanding of strawberry quality formation mechanisms and provides critical theoretical targets for molecular breeding. • The contents of SA, BR, EBL, GA 5 and GA 19 accumulated from the SG to BG stage. • The contents of ABA and MT were relatively high from the W to the R stage. • Sucrose was positively correlated with ABA but negatively correlated with FaARF2 . • ABA positively while GA₃ negatively correlated with malic acid accumulation. • AsA was positively correlated with SA, EBL, GA 14 , FaTCP7 , FaNAC73 , FaARF2 and FaCMB1 .