euAP2a, a key gene that regulates flowering time in peach () by modulating thermo-responsive transcription programming.

Frequent spring frost damage threatens temperate fruit production, and breeding of late-flowering cultivars is an effective strategy for preventing such damage. However, this effort is often hampered by the lack of specific genes and markers and a lack of understanding of the mechanisms. We examined a Late-Flowering Peach () germplasm and found that its floral buds require a longer chilling period to release from their dormancy and a longer warming period to bloom than the control cultivar, two key characteristics associated with flowering time. We discovered that a 983-bp deletion in , an ()-related gene with known roles in regulating floral organ identity and flowering time, was primarily responsible for late flowering in . This deletion disrupts an miR172 binding site, resulting in a gain-of-function mutation in . Transcriptomic analyses revealed that at different stages of floral development, two chilling-responsive modules and four warm-responsive modules, comprising approximately 600 genes, were sequentially activated, forming a unique transcription programming. Furthermore, we found that was transiently downregulated during the activation of these thermal-responsive modules at various stages. However, the loss of such transient, stage-specific downregulation of caused by the deletion of miR172 binding sites resulted in the deactivation or delay of these modules in the flower buds, suggesting that acts as a transcription repressor to control floral developmental pace in peaches by modulating the thermo-responsive transcription programming. The findings shed light on the mechanisms behind late flowering in deciduous fruit trees, which is instrumental for breeding frost-tolerant cultivars.