The Molecular Evolution Analysis Of Genes Related With Cotton Fiber Development In Different Cotton Species In Gossypium

Cotton from the genus Gossypium is the world's most important fiber crop plant. For nearly 100 years, a wide variety of data, including morphologic, meiotic, karyotypic, genetic and molecular, were generated to address the relationships among members of the genus. Now, the most authoritative classification for Gossypium follows Fryxell (1992), who divided Gossypium into four subgenera, eight sections, nine subsections and approximately 50 species. Forty-five cotton species are diploid and five are tetraploid. The five tetraploid species are of allopolyploid origins, originated from interspecific hybridization between diploid A- and D-genome species, the best extant model of the A-subgenome donor is G. herbaceum, while the D-subgenome donor remained unclear. So, in this study, based on the sequence and the structures of 16 fiber development genes in 16 cotton species, we revealed the relationship of 13 diploid D-genome species and the D-genome donor of tetraploid species.16 fiber development genes, including 15 accessioned to NCBI and a new sucrose synthase gene(SusA1) cloned by our lab, were chose to study. First, we cloned these genes in the genome DNA of 16 cotton species, including one diploid A-genome species,13 diploid D-genome species and two tetraploid species. In the orthologues and homoelogous loci of 16 studied genes, the sequence and structure of 13 genes were conservative and 3 genes(ManA2, CelA3 and CIPK1) were diverse. The evolution rates between A and D-genome and between A (D)-genome and A (D)-subgenome revealed that the same gene may have same rates among different species and evolution rates were divergence among genes; D-subgenome of allotetraploid had higher evolution rate than A-subgenome, and Hai7124 may be more conserved than TM-1. Further, the phylogenetic trees of each gene were constructed. The results of 11 genes showed that 13 D-genome species were congruent with Fryxell's subsection taxonomy, while 5 genes, ACT1, CelA3, LTP3, Susl and Pel, were different. And except Expl and SusAl, the other 14 genes were independent evolution between A- and D-subgenome in the allopolyploid after polyploid formation. For 12 genes, the D-subgenomes of TM-1 and Hai7124 had closer relationship with G. raimondii, while D-subgenomes of ACT1, Exp, POD2 and Pel were in the same cluster with other diploid D-genome species. Further, the phylogenetic tree was constructed based on the combined sequence data. The results showed that 13 D-genome species were congruent with Fryxell's subsection taxonomy, the A- and D-subgenome in the allopolyploid were independent evolution after polyploid formation and G. raimondii has the closest gnetic relationship with the D-genome donor of G. hirsutum and G. barbadense.