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How eukaryotic pathogens explore the fitness landscape by mitotic recombination

真核病原体如何通过有丝分裂重组探索适应性景观

基本信息

批准号：
8489735
负责人：
Tim James
金额：
$ 23.33万
依托单位：
UNIVERSITY OF MICHIGAN AT ANN ARBOR
依托单位国家：
美国
项目类别：
财政年份：
2013
资助国家：
美国
起止时间：
2013-01-15 至 2014-12-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8489735
关键词：
Address Alleles Animal Model Antifungal Therapy Biocompatible Materials Cell Separation Chromosomes Data Development Diploidy Environment Eukaryota Event Evolution Gene Mutation Genes Genetic Genetic Drift Genetic Load Genetic Recombination Genetic Variation Genome Genomics Genotype Goals Green Fluorescent Proteins Growth Habitats Haploidy Health Human Infection Larva Life Life Cycle Stages Loss of Heterozygosity Malignant Neoplasms Maps Meiosis Methods Microbe Mitosis Mitotic Recombination Modeling Molecular Epidemiology Moths Mutation Natural Selections Nucleotides Organism Pathogenesis Pathogenicity Island Phenotype Play Population Population Genetics Population Sizes Process Reactive Oxygen Species Relative (related person)Research Role Saccharomyces cerevisiae Speed Staging System Temperature Testing Variant Virulence Virulence Factors Waxes Work Yeast Model System Yeasts asexual base empowered epidemiology study fitness in vivo interest next generation sequencing novel pandemic disease pathogen positional cloning public health relevance research study sample fixation sex stressor theories tumorigenesis

项目摘要

DESCRIPTION (provided by applicant): Mitotic recombination occurs in all diploid organisms, but its evolutionary significance has largely been ignored. Mitotic recombination causes loss of heterozygosity (LOH), making it counterintuitive that it could be adaptive. In large multicellular organisms, LOH is considered primarily maladaptive and is frequently associated with tumorigenesis. Yet in organisms with a free-living haploid stage that lack a high genetic load, such as many unicellular fungal and protozoan pathogens, LOH it is likely to be an important mechanism speeding the fixation of beneficial recessive alleles. This assumption is reinforced by studies of natural populations of diploid pathogens that consistently show evidence for polymorphic LOH genomic regions. These observations indicate that LOH is pervasive, however there is a critical need to address whether, under what conditions, and by what mechanisms LOH is an essential component of how diploid pathogens explore their fitness landscapes. Our central hypothesis is that LOH is an important component of evolution by positive selection, but the relative importance of LOH as an adaptive force will be positively correlated with the heterozygosity of the initial genotype or population. We are particularly interested in applying this to the fitness landscape of pathogens because they are notoriously clonal, at least 1,500 described pathogenic protozoon species are diploid, and pathogens appear to have increased rates of LOH in vivo. Here we propose a novel method to test whether heterozygosity speeds the rate of adaptation by mitotic recombination using a yeast-wax worm (Saccharomyces cerevisiae-Galleria mellonella) pathogenesis model. Aim 1 will clonally evolve replicate populations growing inside waxworm larvae initiated from single parental genotypes differing over a 32-fold range of heterozygosity. Using fluorescent cell sorting based on a green fluorescent protein tagged yeast, we will be able to extract pure yeast populations from the infected larvae after 48 hrs of in vivo growth, and this process will be repeated for 100 serial transfers. Cell sorting also allows pathogen fitness to be estimated at each transfer, allowing us to test whether the rate of adaptation is correlated with initial heterozygosity. Aim 2 will use next generation sequencing to genotype the evolved lines to identify parallel LOH events among replicate populations that indicate the action of positive selection and identify virulence genes. Using this experimental evolution approach will allow us to avoid the problems associated genetic drift and mutation accumulation due to small population sizes. Development of the yeast-Galleria infection model into an experimental evolution system will provide a means to map the relationship between pathogen genotype, virulence, and fitness in more powerful way than standard reverse genetic approaches.

描述（由申请人提供）：