부산대학교 도서관

Upon assembling the first Gossypium herbaceum(A1) genome and substantially improving the existing Gossypium arboreum(A2) and Gossypium hirsutum((AD)1) genomes, we showed that all existing A-genomes may have originated from a common ancestor, referred to here as A0, which was more phylogenetically related to A1than A2. Further, allotetraploid formation was shown to have preceded the speciation of A1and A2. Both A-genomes evolved independently, with no ancestor–progeny relationship. Gaussian probability density function analysis indicates that several long-terminal-repeat bursts that occurred from 5.7 million years ago to less than 0.61 million years ago contributed compellingly to A-genome size expansion, speciation and evolution. Abundant species-specific structural variations in genic regions changed the expression of many important genes, which may have led to fiber cell improvement in (AD)1. Our findings resolve existing controversial concepts surrounding A-genome origins and provide valuable genomic resources for cotton genetic improvement.