Submitted to: Plant Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2018
Publication Date: 6/18/2018
Citation: Lu, S., Faris, J.D., Edwards, M.C. 2018. Molecular cloning and comparative analysis of a PR-1-RK hybrid gene from Triticum urartu, the A-genome progenitor of hexaploid wheat. Plant Molecular Biology. https://doi.org/10.1007/s11105-018-1098-7.
Interpretive Summary: Plants are subject to various types of biotic and abiotic stresses, such as infection by pathogens or soils with high salinity levels. We recently identified two novel genes from common wheat that encode proteins potentially involved in controlling the wheat plant’s response to such stresses. Common (or bread) wheat is derived from natural crosses between several wild ancestors, one of which is a wild wheat relative known as Triticum urartu. In this study, we wished to characterize stress-related genes from T. urartu and found that this plant species has a functional gene related to its counterparts in common wheat, but that it also has a truncated, nonfunctional form of the gene. Studies indicated that the functional gene is expressed and up-regulated by salt stress, and that plants lacking this gene are more sensitive to salt stress. This study provides important information regarding the evolutionary origin of these wheat genes and provides additional evidence that this type of gene may play an important role in adaptation to salinity stress. Future studies on this group of genes should help identify new genetic resources for wheat crop improvement.
Technical Abstract: Wheat genomes encode pathogenesis-related protein 1 (PR-1)/receptor-like kinase (RK) hybrid proteins as first reported for hexaploid wheat. To date, no PR-1-RK-like proteins have been identified in the diploid wild wheat Triticum urartu, the A-genome progenitor of hexaploid wheat. Here we report the cloning and characterization of a PR-1-RK hybrid gene (TuPr-1-rk) and a related pseudogene (TuPr-1-rkP) from T. urartu and comparative analysis of the wheat Pr-1-rk genes. TuPr-1-rk and TuPr-1-kP were found to distribute independently among the natural populations of T. urartu, and the accession G1812 (the source of the published genome) was found to contain TuPr-1-rkP only. Sequence analysis revealed that TuPr-1-rkP originated from TuPr-1-rk through repetitive DNA-associated recombination. Transcriptional analysis confirmed that TuPr-1-rk is expressed in response to salinity stress and is subjected to alternative splicing (AS) as are the Pr-1-rk genes in hexaploid wheat, whereas TuPr-1-rkP is completely silenced. Thirteen AS-derived TuPr-1-rk mRNA isoforms were identified, and a comparable abundance was found between one encoding the full-length protein and those encoding C-terminally truncated proteins. Comparative analysis revealed that the wheat PR-1-RK proteins are highly conserved despite the substantial genomic variations of the coding genes. The identification of the TuPr-1-rk gene adds an important ancestral member to the wheat PR-1-RK gene family, and the observed commonality in expression patterns and the conservation of the PR-1-RK proteins support the notion that the Pr-1-rk gene may play important roles in stress response-related pathways in wheat.