Cloning and Expression Analysis of PAP1 in Brassica juncea

Anthocyanins are important substances accounting for the leaf color in Brassica juncea and PAP1  gene is one of the key transport factors in the anthocyanin synthesis pathway. In this study, homologous cloning technology was used to clone the PAP1  gene sequences of Brassica juncea  with different leaf colors. Specific primers were designed according to the gene sequences of Brassica rapa  with high homology for PCR amplification. The PAP1  gene of Brassica juncea  is 1 348 bp~1 669 bp long, and the coding region sequence is 744 bp~753 bp, including 3 exons and 2 introns. Two MYB blinding domains are found in PAP1 protein at the site of 9~59 and 62~110 amino acids. Phylogenetic analysis showed that the PAP1  gene of Brassica juncea  had high homology with the related genes of Brassica rapa  and Brassica rapa subsp. rapa, but had low homology with Arabidopsis thaliana . Compared gene sequences in Brassica juncea  with different leaf colors, there are no differences between the coding sequence of purple and red leaf Brassica juncea , but the encoded protein have 22 amino acid differences from green leaves. We also observed the lower expression level of PAP1  and its related target genes such as DFR , TT19  in green leaves, which may lead to the differences of leaf color in Brassica juncea . This study provides a reference for exploring the function of PAP1  gene and the formation mechanism of different leaf color of Brassica juncea .