Abstract: The mitogen-activated protein kinase 4（MAPK4）c DNA were isolated from the stigma of ornamental kale（Brassica oleracea var.acephala）self-incompatibility line(S_13-bS_13-b)by RT-PCR.The obtained Bo MAPK4c DNA contained a 1 122 bp open reading frame in length,encoded 373 amino acids,and had a serine/threonine domain,no signal peptide and transmembrane structure.The deduced amino acid sequence of Bo MAPK4 shared 99.7%,99.5%and 95.4%identity with Brassica napus Bn MAPK4,Brassica rapa Br MAPK4,Arabidopsis thaliana At MAPK4,respectively.The ORF of Bo MAPK4 was constructed into the prokaryotic expression vector p ET-14b and transformed into Escherichia coli BL21（DE3）for expression.SDS-PAGE showed that Bo MAPK4 protein was specifically expressed at a molecular weight of 45 k Da.The recombinant Bo MAPK4 was obtained by affinity chromatography,and the polyclonal antibody against Bo MAPK4 was prepared by immunizing mice.The total proteins of sepals,petals,anthers,stigmas,styles and ovaries of ornamental kale were extracted,and protein expression was detected by Western blot.The results showed that Bo MAPK4 was less expressed in petals,anthers and ovary,more expressed in sepals and styles,and the highest expressed in stigmas.The study lays the foundation for exploring the biological functions of Bo MAPK4.