Dormancy Dynamics in Japanese Plum: Transcriptomic Responses to Variable Climatic Conditions and Chill Requirements

Dormancy progression in temperate fruit trees is highly sensitive to environmental conditions and chilling accumulation. To investigate the regulation of dormancy in Japanese plum ( Prunus salicina hybrids), we performed a comparative transcriptomic analysis of flower buds from two Japanese plum cultivars with different chilling requirements, "Hiromi Red" (high chill) and "Crimson Glo" (low chill), grown under contrasting climatic climates (semi-arid and Mediterranean subtropical). The study combined phenological observations, quantification of chill and heat requirements, as well as transcriptomic analyses across three key developmental stages: full dormancy (T0), dormancy release (T1), and full recovery (T2). Climate exerted a stronger influence than dormancy stage on gene expression profiles, leading to cultivar- and climate-specific transcriptional responses. Key dormancy-related genes—such as DAM , FT , and SAP1 — exhibited differential expression patterns across climates, suggesting roles in climatic adaptation. Notably, dormancy phases occurred approximately one month earlier under Mediterranean subtropical conditions, accompanied by a marked reduction in chilling requirements. Expression and phylogenetic analyses revealed that environmental conditions had a stronger effect on the transcriptomic profiles than the progression of dormancy itself, potentially due to epigenetic modulation. These findings provide new insights into the molecular mechanisms underlying dormancy in woody perennial species and offer perspectives for developing cultivars better adapted to changing climatic scenarios. Gene & Accession Numbers All sequence data and genome files generated for this study were deposited in the NCBI Sequence Read Archive (SRA) under BioProject PRJNA1276976.