Auxin is an important phytohormone through plant growth and development. Aux/IAA protein, as a core component in the auxin signaling pathway, plays a vital role in various biological processes such as flower development and floral volatile metabolism in many plants. However, there were a few studies on the Aux/IAA gene family in Prunus plants in Rosaceae and expression patterns of PmIAAs in P. mume. Here, we identified a total of 108 RoIAA gene family members in four typical Rosaceae plants, which included 22 PmIAAs from P. mume, 22 PpIAAs from Prunus persica, 31 PdIAAs from Prunus dulcis and 33 PaIAAs from Prunus armeniaca. Subsequently, the results of the phylogenetic analysis of Aux/IAAs showed that they were categorized into ten groups, and gene structures and motifs were conservative in each group, suggesting that RoIAAs in Rosaceae species had a strong relationship. However, the physical distributions of RoIAAs on chromosomes of every species showed completely uneven. Gene duplications suggested that seven pairs of PmIAAs, eleven pairs of PpIAAs, eleven pairs of PdIAAs, and three pairs of PaIAAs suffered from tandem and segmental duplications. Moreover, the results of the synteny analysis indicated that RoIAAs in four Rosaceae species might come from one ancestor. To explore the roles of PmIAAs in P. mume, expression patterns in five tissues and at four flowering development stages were performed. The results showed that PmIAAs variously expressed in five tissues and five genes (PmIAA2, −9, −10, −12, and −15) might affect flower development and the synthesis of floral compounds in P. mume. This study provided valuable information for further elucidating the regulatory function of PmIAAs in metabolism processes in P. mume.

Chaenomeles speciosa, a plant species with high ornamental value, exhibited significant darkening of its petal coloration under drought conditions. This chromatic alteration primarily stems from anthocyanin biosynthesis and transport. Through integrated proteomic and transcriptomic analyses, we identified CsABCG6, a transporter of the ABCG subfamily, as a key regulator. The molecular docking analysis preliminarily demonstrated that CsABCG6 bound to anthocyanin monomers. Functional characterization revealed a dual role of CsABCG6 in regard to anthocyanin metabolism; it displayed anthocyanin transport activity in yeast systems, whereas transient transformation assays confirmed its capacity to enhance anthocyanin biosynthesis. Stable transformation experiments in tobacco further validated the anthocyanin-promoting function of the previously identified transcription factor CsMYB6. Yeast one-hybrid (Y1H) and dual-luciferase assays (LUC) established that CsMYB6 transcriptionally activates the CsABCG6 promoter, thus collectively defining the CsMYB6-CsABCG6 signaling module as a critical mechanism for the precise dynamic regulation of anthocyanin metabolism under drought stress.