Genome-wide identification and analyses of bHLH family genes in Brassica napus

The bHLH (basic/helix-loop-helix) protein is one of the largest transcription factors (TFs) that is essential in regulating plant growth and development. Although the bHLH family has been identified in some organisms, a systemic study has not been performed in Brassica napus, which is the third most important oilseed crop worldwide. In the present study, a total of 460 bHLH TFs were identified from the genome of B. napus and clustered into 25 subfamilies. Structural analysis was used to identify the DNA binding type and conserved amino residues of the identified sequence in the bHLH domain. In addition, a comparative genomic analysis of B. napus and its progenitors (Brassica rapa and Brassica oleracea) and two basal angiosperms (Amborella trichopoda and Vitis vinifera) was performed to trace the change during expansion and evolution of the bHLH family. The bHLH TFs in leaves and roots showed various expression patterns. The homologs of the AA-subgenome and CC-subgenome exhibited similar expression patterns, but were more divergent between the homologs caused from other duplicate events.