In this study, transcriptome analyses were carried out on the fruits of Kurakato Wase peach and its early-ripening mutant at different developmental stages. The key factors involved in fruit ripening regulation were explored, so as to provide a theoretical basis for further study on the regulation mechanism of fruit ripening.

The flesh of Kurakato Wase peach and its early-ripening mutant was sampled at 30 d, 45 d, 59 d, 71 d, and 89 d after anthesis, and transcriptome analyses were performed on the above samples. The candidate differentially expressed genes (DEGs) were verified by quantitative real-time PCR (qRT-PCR). The biological function of DEGs were analyzed through GO function and KEGG pathway. The weighted gene co-expression network analysis (WGCNA) was constructed to identify the hub modules and hub genes closely related to fruit ripening.

Four comparison groups including y1 vs c1, y2 vs c2, y3 vs c4 and y4 vs c5 were obtained based on fruit development stages. A tatal of 4 395 DEGs were identified with 2 212 up- and 2 183 down-regulated genes. There were 10, 11 and 18 candidate genes involved in ethylene, abscisic acid and auxin synthesis and signal transduction, respectively. The interaction networks between 10 IAA proteins and their predictive interacting proteins ARF were constructed. GO function revealed that the DEGs were mainly enriched in cellular processes, metabolic processes and monomeric processes in the biological process category; in cell component category, DEGs were mainly enriched in membranes and cellular components; in molecular function category, DEGs were mainly enriched in binding protein and catalytic activity. There were more DEGs in comparison groups y3 vs c4 and y4 vs c5, and these DEGs mainly enriched in molecular functions, such as binding and catalytic activity. The KEGG pathway analysis showed that a variety of secondary metabolites changed during fruit development and ripening, such as sesquiterpene and triterpenoid biosynthesis, flavonoid biosynthesis, carotenoid biosynthesis, and α-linolenic acid metabolism. In addition, auxin signal transduction pathway was found to be enriched at different time nodes.

Among DEGs, a large number of hormone signal transduction pathway genes, especially auxin signal pathway genes, were enriched, and these genes might play an extremely important role during fruit ripening. The functions of candidate genes IAA and ARF and the molecular regulation of fruit ripening would be further elucidated in the future studies.