Correlation Analysis Of Whole Genome Duplication And Chromosome Karyotype Evolution In Yeasts

Whole genome duplication is a core event of eukaryotic evolution.The whole genome duplication of yeast species occurred about 100 million years ago,making the basic number of yeast chromosome varied from 8 to 16.However,chromosome number of polyploid yeasts was 10 to 16 and that of yeast without polyploidization was 6 to 8,which indicated that the genomic structure and chromosome karyotype of yeasts in the evolution process had undergone complex changes.The homologous genomic structure analysis of 8 yeast species showed that paralogous genes of the polyploid genomes were gained and the whole genome duplication resulted in 20% genes in each genome.After homologous chromosome fragments were grouped according to the similarity,homologous genes information associated with polyploidy and species differentiation was obtained.As a random phenomenon,gene losses were accumulated with time and the missing chromosome fragments was extended,length distribution of which was a geometric distribution.Another finding was that polyploid yeasts had a heterologous polyploid ancestor.The evolution mechanism of genome karyotype from ancestor yeasts to modern yeasts was analyzed.Results showed that the decrease of yeast chromosomes was due to chromosomes fusion,which was accompanied by the formation of microchromosomes and the loss of centromeres.The homology presetation among chromosomes indicated that the chromosome karyotypes of L.kluveri and polyploid S.cerevisiae was both closer to their ancestral karyotypes.Mealwhile,karyotypic evolution analysis revealed that the chromosomal karyotypes of yeast undergoing whole-genome-duplication changed greater.In conclusion,multi-reference and multi-level homologous collinearity information was constructed and the change of chromosome karyotype from ancestor yeasts to modern yeasts was analyzed,which provided the basic platform for comparative genomic research of yeasts.