Molecular evolution and genome-wide analysis of the SBP-box family in cucumber (Cucumis sativas)

SQUAMOSA promoter binding protein (SBP)-box gene family encodes a group of transcription factors that play essential roles in plant development and stress responses. However, the SBP-box gene family has not been well characterized in cucumber (Cucumis sativas). In the present study, we identified 15 putative SBP-box genes (CuSBPs) distributing on 4 chromosomes of cucumber. Evolutionary analysis showed that the green plant SBP family originated from liverworts. Phylogenic analysis divided CuSBPs into 6 groups similar to those of Arabidopsis and rice. Intron–exon and motif structure within each group shared common features. Expression pattern analysis of transcriptional data for flowering demonstrated conserved CuSBPs function in vegetative-to-reproductive transition. Gene expression of cucumber leaves in response to powdery mildew showed that conserved CuSBPs function in regulatory pathways such as hormone regulation pathways. Moreover, codon bias analysis explained the mutation and selection pressure exerted on SBP-box genes. This study comprehensively characterized cucumber CuSBP gene family, which is likely to provide a foundation to explore the functions of CuSBPs for improving yield, quality and stress tolerance of cucumber in the future