Cloning and characterization of a rapid alkalinization factor gene BrRALF1 in Chinese cabbage.

Analysis of gene differential expression was performed by cDNA-AFLP in the genic male sterile line AB02 of Chinese cabbage.A differentially expressed cDNA fragment,TDF-3,was found only in fertile plants.The full-length cDNA of the gene related with TDF-3 was amplified by RACE and RT-PCR.The cDNA was 551 bp long,encoding rapid alkalinization factor of 79 amino acids with a signal tide of 28 amino acids.Mature BrRALF1 protein contained one conserved YIXY domain,one YXRGC domain and four cysteines which can form disulfide bonds.Five post-translational modification sites were predicted in mature BrRALF1 protein.BrRALF1 only expressed in big and middle floral buds of the fertile plants in AB02,not in male sterile plants.Tissue expression profile analysis indicated that BrRALF1 expressed in filaments,anthers,sepals,pistils,petals of fertile flowers,and the peak expression occurred in anthers.BrRALF1 expression was inhibited in male plants.