Recombination Promoters

Novel Genetics Stocks for Chromosome-wide Enhancement of Genetic Recombination

Project Summary:

Novel gene transfers from wild wheat relatives to hexaploid bread wheat is restricted due to predominance of homologous recombination. The presence of Pairing homoeologous 1 (Ph1) gene in the 5BL arm of the wheat chromosome allows only homologous chromosomes to pair and recombine. Previously we have identified a novel homoeologous pairing promotor gene(s) (Hpp-5Mg) found on chromosome 5Mg of Aegilops geniculata which will freely recombine with wheat homoeologous chromosome 5D in the presence of Ph1. We also investigated the effect of Hpp-5Mg on homoeologous recombination in absence of Ph1. In Hpp-5Mg/ph1bph1b plants we observed genome-wide increase in homoeologous recombination and multiple crossover (CO) breakpoints including CO breakpoints in proximal regions, where recombination is usually suppressed. We tested the efficacy of Hpp-5Mg/ph1bph1b-induced homoeologous recombination by producing new recombinants for wheat streak mosaic virus resistance gene, Wsm3 present in wheat-Thinopyrum intermedium Robertsonian translocation (RobT T7BS.7S#3L). Genomic in situ hybridization-based progeny screening of the recombinants revealed that 6.5% were wheat-Th. intermedium recombinants, which is about 100-fold higher compared with the recombinant frequency of 0.06% observed using ph1b-induced homoeologous recombination without Hpp-5Mg in (RobT) T7BS. 7S#3L. We identified the putative Hpp-5Mg region within the distal 30 percent of the 5Mg long arm. In this project we propose to identify novel 5Mg/ph1b stocks carrying smaller chromosome segments (less than 30 percent) harboring the Hpp-5Mg gene(s). These novel genetic stocks with smaller Ae. geniculata segments carrying Hpp-5Mg gene(s) will be useful to accelerate the biotic and abiotic gene transfer from wild relatives to the cultivated wheat cultivars in wheat crop improvement programs. Also, these novel genetic stocks provide the foundation for further molecular analysis and fine-mapping of Hpp-5Mg gene(s). In addition, we also propose to test the effect of Hpp-5Mg on shifting the recombination spots from distal to proximal region of the chromosome using immunofluorescence assay and map the CO breakpoints.