A study of the mechanisms of meiosis in wheat

Breeding programs have the objectives to develop more productive and more stable varieties. Hybridization and selection are frequently employed in plant breeding and the success of introgression of special traits such as disease resistance relies on genetic recombination between the host and alien chromosomes. During meiosis, homologous chromosomes recognized each other, align and pair which ensure their recombination and correct segregation at metaphase. This process controls aberrant chromosome number within the gametes, and ensures that genes are shuffled by recombination. 70% of flowering plants are polyploids including bread (hexaploid) and pasta wheat (tetraploid), and strict homologous pairing in species containing more than one genome is even more important. Wheat homologous chromosomes and their relative homoeologues are genetically close enough to pair during meiosis, however, the Ph1 locus ensures that only true homologues pair and recombine, stabilizing the wheat genome. Because the pairing is exclusive to homologues, alien chromosomes cannot recombine with wheat chromosome and are eliminated. Deletion lines for the Ph1 locus, allowing recombination of wheat and its relatives, are used for new wheat variety production.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

A study of the mechanisms of meiosis in wheat

Breeding programs have the objectives to develop more productive and more stable varieties. Hybridization and selection are frequently employed in plant breeding and the success of introgression of special traits such as disease resistance relies on genetic recombination between the host and alien chromosomes. During meiosis, homologous chromosomes recognized each other, align and pair which ensure their recombination and correct segregation at metaphase. This process controls aberrant chromosome number within the gametes, and ensures that genes are shuffled by recombination. 70% of flowering plants are polyploids including bread (hexaploid) and pasta wheat (tetraploid), and strict homologous pairing in species containing more than one genome is even more important. Wheat homologous chromosomes and their relative homoeologues are genetically close enough to pair during meiosis, however, the Ph1 locus ensures that only true homologues pair and recombine, stabilizing the wheat genome. Because the pairing is exclusive to homologues, alien chromosomes cannot recombine with wheat chromosome and are eliminated. Deletion lines for the Ph1 locus, allowing recombination of wheat and its relatives, are used for new wheat variety production.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The low recombining pericentromeric region of barley restricts gene diversity and evolution but not gene expression

The low-recombining pericentromeric region of the barley genome contains roughly a quarter of the genes of the species, embedded in low-recombining DNA that is rich in repeats and repressive chromatin signatures. We have investigated the effects of pericentromeric region residency upon the expression, diversity and evolution of these genes. We observe no significant difference in average transcript level or developmental RNA specificity between the barley pericentromeric region and the rest of the genome. In contrast, all of the evolutionary parameters studied here show evidence of compromised gene evolution in this region. First, genes within the pericentromeric region of wild barley show reduced diversity and significantly weakened purifying selection compared with the rest of the genome. Second, gene duplicates (ohnolog pairs) derived from the cereal whole-genome duplication event ca. 60MYa have been completely eliminated from the barley pericentromeric region. Third, local gene duplication in the pericentromeric region is reduced by 29% relative to the rest of the genome. Thus, the pericentromeric region of barley is a permissive environment for gene expression but has restricted gene evolution in a sizeable fraction of barley's genes