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Ethylene plays an important role in regulating the development and ripening of fruits, and 1-aminocyclopropane carboxylic acid synthase is the key rate-limiting enzyme in ethylene synthesis pathway. In this study, eight PpACS genes were identified from the peach genome [Prunus persica (L.) Batsch], and their phylogeny, gene structures, promoter motifs and expression patterns were analyzed. The PpACS genes could be divided into four types, and the genes with similar structures and motif distribution clustered together. Identification of the cis-elements in the promoters revealed that the PpACS genes may respond to various hormones. Furthermore, expression analysis showed that five (PpACS1, PpACS5, PpACS6, PpACS7 and PpACS8) of the eight PpACS genes were expressed at different stages during peach fruit development. Among them, PpACS1 was highly expressed at the ripening stage and induced by ethylene. The expression peaks of PpACS5, PpACS6, PpACS7 and PpACS8 during the transition from first exponential growth to pit hardening (S1 to S2) indicated a potential function of ethylene during this important transition. Taken together, these results provide valuable information for future investigation into the functions of the PpACS genes during peach fruit development and ripening.

Anthocyanins, a categories of metabolites derived from flavonoid biosynthesis pathway, are responsible for the red color of peach. Anthocyanin metabolism is modulated by a complicated regulatory network. In this study, our results demonstrated that PpNAC25 was a component of anthocyanin regulatory network in peach. PpNAC25 showed a closed relationship with the well-known ripening-related gene NOR (no-ripening) and was highly expressed in peach fruit. Overexpression of PpNAC25 in poplar resulted in a redder shoot tips compared with EV control. PpNAC25 overexpression upregulated the anthocyanin biosynthetic and transportation genes in transcript levels and then increased anthocyanin contents. In Y1H and Luc/Ren assay, PpNAC25 bound to the promoter of the anthocyanin-activator PpMYB10.1 and PpMYB10.2 and activated its transcript. Moreover, PpNAC25 formed a heterodimer with PpNAC1, an anthocyanin-regulator. Our researches provide evidence that PpNAC25 may be a positive regulator of anthocyanin biosynthesis in peach fruit.