Genome-wide identification of BBX gene family and their expression patterns under salt stress in soybean

Background: BBX genes are key players in the regulation of various developmental processes and stress responses, which have been identified and functionally characterized in many plant species. However, our understanding of BBX family was greatly limited in soybean. Results: In this study, 59 BBX genes were identified and characterized in soybean, which can be phylogenetically classified into 5 groups. GmBBXs showed diverse gene structures and motif compositions among the groups and similar within each group. Noticeably, synteny analysis suggested that segmental duplication contributed to the expansion of GmBBX family. Moreover, our RNA-Seq data indicated that 59 GmBBXs showed different transcript profiling under salt stress, and qRT-PCR analysis confirmed their expression patterns. Among them, 22 GmBBXs were transcriptionally altered with more than two-fold changes by salt stress, supporting that GmBBXs play important roles in soybean tolerance to salt stress. Additionally, Computational assay suggested that GmBBXs might potentially interact with GmGI3, GmTOE1b, GmCOP1, GmCHI and GmCRY, while eight types of transcription factors showed potentials to bind the promoter regions of GmBBX genes. Conclusions: Fifty-nine BBX genes were identified and characterized in soybean, and their expression patterns under salt stress and computational assays suggested their functional roles in response to salt stress. These findings will contribute to future research in regard to functions and regulatory mechanisms of soybean BBX genes in response to salt stress.