Submitted to: Molecular Genetics and Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 30, 2011
Publication Date: April 23, 2011
Citation: Lu, S., Friesen, T.L., Faris, J.D. 2011. Molecular characterization and genomic mapping of the pathogenesis-related protein 1 (PR-1) gene family in hexaploid wheat (Triticum aestivum L.). Molecular Genetics and Genomics. 285:485-503. Interpretive Summary: A group of related plant genes known as pathogenesis-related protein 1 (PR-1) genes are induced in plants challenged by microbial pathogens (fungi, bacteria, viruses and nematodes) or insects, and are associated with disease resistance. PR-1 genes are known to exist in multigene families in plants with relatively simple genomes such as rice, but have not been well studied in plants with more complex genomes such as common bread wheat. The objective of this study was to characterize the PR-1 gene family in bread wheat, which possesses one of the largest genomes among crop plants. We determined the DNA sequences of 23 wheat PR-1 genes, developed specific assays (markers) for each of these genes, and determined the chromosomal locations for all 23 genes. The full-length DNA sequences of wheat PR-1 genes obtained in this study provide critical information for further genome-wide characterization of the wheat PR-1 gene family. The markers and chromosome mapping information resulting from this study provide a solid foundation for conducting further studies to evaluate the roles of individual PR-1 genes in governing disease resistance. Such studies will also lead to a better understanding of how PR-1 genes function to confer resistance, and possibly lead to the development of novel methods for engineering disease resistant crops.
Technical Abstract: The group 1 pathogenesis-related (PR-1) proteins, known as hallmarks of defense pathways, are encoded by multigene families in plants as evidenced by the presence of 22 and 32 PR-1 genes in the finished Arabidopsis and rice genomes, respectively. Here, we report the initial characterization and mapping of 23 PR-1-like (TaPr-1) genes in hexaploid wheat (Triticum aestivum L.), which possesses one of the largest (>16,000 megabases) genomes among monocot crop plants. Sequence analysis revealed that the 23 TaPr-1 genes all contain intron-free open reading frames that encode a signal peptide at the N-terminus and a conserved PR-1-like domain. Phylogenetic analysis indicated that TaPr-1 genes form three major monophyletic groups along with their counterparts in other monocots; each group consists of genes encoding basic, basic with a C-terminal extension, and acidic PR-1 proteins, respectively, suggesting diversity and conservation of PR-1 gene functions in monocot plants. Mapping analysis assisted by untranslated region-specified discrimination (USD) markers and various cytogenetic stocks located the 23 TaPr-1 genes to seven different chromosomes, with the majority mapping to chromosomes of homoeologous groups 5 and 7. Together, the genomic mapping and phylogenetic analyses provided insights to the origin, evolution, and homoeologous relationships of the TaPR-1 genes. The data presented provide critical information for further genome-wide characterization of the wheat PR-1 gene family and the USD markers developed will facilitate genetic and functional analysis of PR-1 genes associated with plant defense and/or other important traits.