Molecular cloning and characterization of a PR-5 like protein gene from Brassica campestris ssp chinensis

Downy mildew caused by Hyaloperonospora parasitica is a serious fungal disease in non-heading Chinese cabbage (Brassica campestris L. ssp. chinensis Makino). Pathogenesis-related 5 (PR-5) genes play an important role in plant resistance to disease invasion. In this study, a gene encoding pathogenesis-related 5-like (PR-5L) protein, named BcPR-5L, was successfully cloned from non-heading Chinese cabbage. The cDNA sequence of BcPR-5L was 747 bp in length. It encoded a protein of molecular mass of 25.78 kDa, an isoelectric point of 4.42, and containing 248 amino acids. Multiple sequence alignment indicated that BcPR-5L protein was highly homologous to other PR-5L proteins identified in 13 different species, with the highest homology to Brassica rapa. We analyzed the subcellular localization of BcPR-5L protein by using onion epidermal cells and found that it was localized in the membrane. Real time quantitative PCR analyses revealed that the expression of BcPR-5L gene was significantly upregulated after H. parasitica infection, and the expression in the resistant cultivar was higher than that in the susceptible cultivar. In summary, our data suggest that BcPR-5L gene may play an important role in the resistance of non-heading Chinese cabbage to H. parasitica infection.