Molecular cloning and characterization of a CBF gene from Capsella bursa-pastoris

A new CBF gene was cloned from Capsella bursa-pastoris(shepherd's purse) by rapid amplification of cDNA ends (RACE). The full-length cDNA of C. bursa-pastoris CBF gene (designated as Cbcbf) was 1034 bp long and contained a 657 bp open reading frame (ORF) encoding a putative DRE/CRT (LTRE)-binding protein of 219 amino acids. The predicted CbCBF protein was found to have a potential nuclear localization signal (NLS) in its N-terminal region followed by an AP2 DNA-binding motif and an acidic C-terminal half that might act as an activator domain. Bioinformatic analysis revealed that Cbcbf strongly resembled other CBF genes from Arabidopsis thaliana (cbf1, cbf2, cbf3) and Brassica napus (Bncbf5, Bncbf 7, Bncbf16 and Bncbf17). Subsequent cold acclimation assay showed that Cbcbf was relevant to cold acclimation. Our study implies that Cbcbf might have similar functions possessed by other CBF genes such as inducing the expression of some cold-regulated genes and increasing plants' freezing tolerance.