Molecular cloning, characterization and expression analysis of BcHHP3 under abiotic stress in Pak-choi (Brassica rapa ssp. Chinensis)

ABSTRACT In this study, BcHHP3 was isolated from Pak-choi; it has an open-reading frame (ORF) of 1044 base pairs, encoding 347 amino acids, a molecular weight of 39.35？kDa, isoelectric point (pI) of 9.08, an instability index of 48.35, and grand average of hydropathicity of 0.382. Multi-alignment and phylogenetic analysis showed that BcHHP3 bears a high similarity to AtHHP2. As predicted by SOMPA and SWISS-MODEL databases, the structure of the BcHHP3 protein is relatively stable and highly conservative. Real-time quantitative polymerase chain reaction (qRT-PCR) analysis showed that BcHHP3 was induced to co-express under cold and abscisic acid (ABA) stresses. The BcHHP3-GFP fusion protein was localized on the cell membrane and nuclear membrane. This work might be useful for future analysis of other HHP-like genes in Pak-choi. Abbreviations: ABA: abscisic acid; AdipoR: adiponectin receptor; bHLH: basic helix–loop–helix; bp: base pair; CA: cold acclimation; CAMTA: Calmodulin-binding transcription activator; CBF: C-repeat binding factor; FT: freezing tolerance; HHP: Heptahelical protein; ICE: inducer of CBF expression; mPR: membrane progestin receptor; MS: Murashige and Skoog; ORF: open-reading frame; pI: isoelectric point; qRT-PCR: real-time quantitative PCR; SA: salicylic acid; WM: molecular weigh