Genome-Wide Identification and Expression Analysis of the bHLH Gene Family in Fragaria vesca and Its Response to Low-Temperature Stress

Fragaria vesca is a highly adaptable diploid model species. Although bHLH transcription factors (TFs) have been widely reported to regulate plant development and stress responses, the bHLH gene family has not been systematically characterized in Fragaria vesca. In this study, we conducted a genome-wide analysis of the bHLH TF family based on the Fragaria vesca v6 genome assembly. A total of 117 FvbHLH genes were identified, and promoter analysis revealed the presence of numerous cis-regulatory elements associated with plant development, hormone signaling, and stress responses. Transcriptome analysis showed that several FvbHLH genes were differentially expressed in leaves and stems under low-temperature stress. The low-temperature expression patterns of selected genes were further validated by reverse transcription quantitative PCR (RT-qPCR). Moreover, heterologous overexpression of FvbHLH86 in Arabidopsis thaliana enhanced cold tolerance by improving reactive oxygen species (ROS) scavenging capacity. These findings provide a valuable foundation for future functional studies of FvbHLH genes and contribute to a better understanding of the molecular mechanisms underlying cold stress responses in Fragaria vesca.