Characterization of nuclear cap binding complex protein genes (CBP20 and CBP80) from Brassica juncea

Abstract

Nuclear cap binding complex proteins, CBP20 and CBP80, participate in mRNA transcript processing and also play an important role in abiotic stress tolerance. Brassica juncea is a major oilseed crop, and in this study, we reported the cloning and characterization of CBP20 and CBP80 genes from this species. A full-length BjCBP20 cDNA of 1075bp was cloned containing an open reading frame of 783bp encoding a polypeptide of 260 amino acids. Two genomic sequences of 1792bp and 1712bp were also cloned for BjCBP20, both of these having eight exons and seven introns. Likewise, 2538bp BjCBP80 sequence was cloned which encoded a protein sequence of 845 amino acids. Two genomic sequences of 5672bp and 5190bp consisting of eighteen exons and seventeen introns were cloned. Bioinformatics analysis of deduced proteins revealed the presence of the signature RRM domain in BjCBP20 and MIF4G domain in BjCBP80. Nuclear localization signal was present in BjCBP20. The phylogenetic analysis revealed less conservation in BjCBP80 than BjCBP20 when compared to proteins from other organisms. Expression analysis by qRT-PCR depicted steady levels of both the proteins in developmental stages. BjCBP80 showed highest expression in young leaves while lowest level of expression of BjCBP20 was seen in mature leaves. Under salt and osmotic stress, BjCBP80 level decreased initially and then regained back to normal levels. In osmotic stress, the BjCBP20 levels decreased while no significant change was observed under salt stress.