Comparative Analysis Of Genome Structure And Ancient Polyploid Types Of Cotton

With the development of sequencing technology,the genomes of four representative species in the genus Gossypium(Gossypium raimondii,Gossypium arboreum,Gossypium hirsutum,and Gossypium barbadense)had been sequenced.Using high-quality genomic sequences,it is possible to deeply analyze the structure of the Gossypium genome and reveal the evolutionary process of the Gossypium genome.Using grape and cacao as reference genomes,comparative genomics studies can be performed on sequenced species of the Gossypium genus.By performing homology comparisons within and between genomes of all involved species,the homology relationship of each genome is displayed using the homology gene dotplot.According to the phylogeny and homology relationships among species,a collinearity gene list associated with evolutionary events was constructed.Using the collinearity gene list and telomere-centered chromosomal recombination mechanism,the genomes of phylogenetic nodes of Malvaceae were constructed,and the evolutionary trajectories of chromosomes was reconstructed.We found that the Malvaceae ancestor genome consists of 12 chromosomes,and the Gossypium ancestor after WGD has 13 chromosomes.By calculating the polyploid gene loss index(P-index)of the diploid cottons,it was inferred that the paleodeploid of Gossypium ancestors was an allopolyploid.Finally,gene trees were constructed from the duplicated genes generated by WGD,it was found that the duplicated genes showed significantly elevated and unbalanced evolutionary rates,which disrupted the topology of the gene tree.The study updated and supplemented the comparative genomics data of Gossypium and provided basic data for related researches on the genome of Gossypium.The karyotype change from ancestral chromosomes to modern chromosomes is shown in detail using graphics,which provided a reference for the karyotype evolution of other species.A statistical method was used to quantify the fluctuation of gene retention difference,which provided a mathematical method for analyzing the type of polyploid.Figure 27;Table 7;Reference 98.