Structure, Evolution, and Expression of the β-Galactosidase Gene Family in Brassica campestris ssp chinensis

Plant beta-galactosidases (EC 3.2.1.23; BGAL) are associated with cell wall biogenesis and modification. beta-Galactosidase isozymes are encoded by the BGAL multigene family in plants. In this study, 16 BcBGAL genes from the Brassica campestris ssp. chinensis (syn. Brassica rapa ssp. chinensis) genome were investigated and compared with those from Arabidopsis thaliana. A comprehensive genome-wide analysis of BcBGAL genes in B. campestris is presented, including their phylogeny, genome localization, gene structure, and expression patterns. Phylogenetic analysis of 16 BcBGAL and 17 AtBGAL proteins from Arabidopsis indicate that the BcBGALs clustered into four major groups, such that genes within the same group had similar exon-intron structures. The 5'-upstream region of BcBGAL genes contained a group of putative cis-acting elements related to stress and plant hormone response. Expression analysis of BcBGAL genes using quantitative reverse transcription-polymerase chain reaction demonstrates that all BcBGAL transcripts could be detected in at least one type of tissue. Some of these transcripts exhibited tissue-specific expression patterns. Our data provided insights on the evolution of the BGAL gene family and a useful reference for further functional analysis in B. campestris.