Characterization of the F-Box Gene Family and Its Expression under Osmotic Stress in Birch

The F-box gene family is abundant in plants and crucial for plant growth and development. However, two questions prevail: Which F-box genes are involved in regulating plant biological processes? How do these genes regulate such biological processes? In this study, we characterized the F-box family and identified 240 F-box genes in birch (Betula platyphylla Suk.) via HMMER analysis. According to the C-terminal conserved domains, the F-box members were divided into 10 subfamilies. Through phylogenetic analysis, the F-box proteins were clustered into eight evolutionary branches. Synteny analyses suggested that the birch F-box gene family exhibits tandem and segmental duplication events. GO annotation analysis revealed that BpF-box proteins respond to stimuli, and regulate the defense response. According to RNA-Seq analysis, we found that 11 differentially expressed genes (DEGs) are responsive to osmotic stress. We performed co-expression analysis on the representative genes, and GO enrichment analysis further revealed that representative plant genes participate in the regulation of hormones, growth, and development. Through qRT-PCR, we found that the representative BpF-box genes are mainly involved in hormone response signaling pathways. It appears that the F-box gene family plays a significant role in the regulation of birch osmotic stress responses through the regulation of different hormones. Our results provided novel insights into the biological function of BpF-box proteins.