Identification of candidate genes associated with male sterility in CMS7311 of heading Chinese cabbage (Brassica campestris L. ssp pekinensis)

Polima (pol) cytoplasmic male sterility (CMS) is reported to be regulated by orf224, but the molecular mechanisms of CMS are less known. In previous research, CMS7311 of heading Chinese cabbage (Brassica campestris L.ssp. pekinensis) was successfully generated from a pol-like CMS, named 77A. To further understand the molecular mechanisms of this male sterility, cDNA-AFLP and qRT-PCR were used to identify genes differentially expressed during flower bud development between cytoplasmic male-sterile plant (Ms) and male-fertile plant (Mf) derived from the hybrid of CMS7311 and a restorer (Rf). Thirty-two transcripts of different fragments (TDFs) of over 80 bp in length were identified using cDNA-AFLP. Among them, ten TDFs were found expressing in Ms bud, and the others expressing in Mf bud. Gene ontology analysis revealed that these genes were involved in stress response, synthesis and metabolism of fatty acid, cell reconstruction, etc. Further, five genes closely related to male sterile were selected and their expression during the flower bud development of Ms and Mf line were investigated by qRT-PCR. Three genes, BcGRP17, BcMS2, and BcPME31, which were necessary for normal male organ development, showed significantly lower expressions in Ms bud; two genes, BcROPGEF8 and BcTNL3, were induced with significantly higher expression in Ms bud by unknown stress and involved in the formation of male sterility. Further work will be focused on cloning these genes and identifying their functions in the male-sterile process of heading Chinese cabbage CMS7311.