The purple-leaf line XY-PL,an advanced recombinant inbred line,was screened out from the progenies of interspecific hybridization between Brassica napus and Brassica juncea,had performance of stable purple leaf phenotype,high anthocyanin content and good agronomic traits and could be potentially used as intermediates for high anthocyanin content breeding programs.To explore the relationship between the purple-leaf trait of XY-PL and its APR2,a key enzyme for sulfur assimilation and metabolism,applying homologous cloning method and XY-PL and green leaf Zhongshuang No.11 (ZS11) as materials three APR2 homologs were successfully isolated,designated as PL-APR2,GL-APR 2.1 and GL-APR2.2 respectively.Results of sequence analyses showed that they encompassed four exons and three introns,the encoded proteins each had a typical chloroplast transport peptide domain and shared 98.2%—99.1% identities among them,and had the closest phylogenetic relationship with APR2 from cruciferous plants.Compared with GL-APR2.1 and GL-APR2.2,PL-APR2 had three amino acid residues (51SLK53) deletion in the chloroplast transport peptide transporter domain,which would affect the transmembrane transport of its precursor proteins and the efficiency of sulfur assimilation and utilization.Overexpression of PL-APR2 in Arabidopsis thaliana demonstrated that all transgenic lines did not exhibit purple-leaf phenotype from generation T0 to T2 perhaps because of the presence of wild-type AtAPR2 in transformation receptor material.Next,the Arabidopsis apr2 mutant will be used as genetic transformation receptor for further function verification and the transport function of chloroplast transport peptide of PL-APR2 will be analyzed deeply.