Genome-wide identification of the DBB gene family in Phoebe bournei reveals its involvement in heat stress response

High temperature poses severe challenges to the physiological homeostasis of Phoebe bournei , which is known as a valuable woody species. Although the roles of DBB proteins in stress adaptation have been characterized in model plants, the functions of this transcription factor family in P. bournei under heat stress remain unclear. This study provides the first comprehensive analysis of the 22 PbDBB genes, including their evolutionary relationships, structural features, and promoter characteristics. Evolutionary analysis suggests that the expansion of the PbDBB gene family is primarily attributable to segmental and tandem duplication events, which may have contributed to functional divergence among members. Promoter analysis revealed an absence of canonical heat shock elements (HSEs), but an enrichment of STRE and MYB cis-elements, suggesting that PbDBB genes may participate in heat responses through a non-canonical regulatory pathway. Correlation analyses integrating physiological traits and gene expression profiles further supported this regulatory pattern. The qRT-PCR, coupled with physiological association analysis, exhibited the expression dynamics of the PbDBB genes, and determined PbDBB5 , PbDBB10 , PbDBB15 , and PbDBB20 as key candidates involved in heat stress response. This study offers a foundation for identifying potential genetic resources to enhance stress tolerance in this timber species.