Molecular characterisation and expression profiling of calcineurin B-like (CBL) genes in Chinese cabbage under abiotic stresses

Calcium signals act as a second messenger in plant responses to various abiotic stresses, which regulate a range of physiological processes. Calcium-binding proteins, like calcineurin B-like (CBL) proteins, belong to a unique group of calcium sensors that play a role in calcium signalling. However, their identities and functions are unknown in Chinese cabbage. In this study, 17 CBL genes were identified from the Brassica rapa L. (Chinese cabbage) database and Br135K microarray datasets. They were used to construct a phylogenetic tree with known CBL proteins of other species. Analysis of genomic distribution and evolution revealed different gene duplication in Chinese cabbage compared to Arabidopsis. The microarray expression analysis showed differential expression of BrCBL genes at various temperatures. Organ-specific expression was observed by RT-PCR, and qRT-PCR analyses revealed responsiveness of BrCBL genes to cold, drought and salt stresses. Our findings confirm that CBL genes are involved in calcium signalling and regulate responses to environmental stimuli, suggesting this family gene have crucial role to play in plant responses to abiotic stresses. The results facilitate selection of candidate genes for further functional characterisation. In addition, abiotic stress-responsive genes reported in this study might be exploited for marker-aided backcrossing of Chinese cabbage.