Distribution of Fiber Genes in Cultivated and Non-Cultivated Cotton Genomes

Commercial cottons such as Upland cotton (Gossypium hirsutum) contain two tetraploid subgenomes (At and Dt) that relate to modern descendants of diploid genome cottons, one cultivated (A) and the other non-cultivated (D). There is evidence that these two genomes do not contribute equally to the phases of fiber development such as fiber initiation, elongation, secondary cell wall deposition, and maturation. Evaluation of available ancestral A- and D-genome cotton sequences (G. arboreum and G. raimondii) revealed that both A (At) and D (Dt) genomes contribute genes to fiber development although the A-genome has more fiber elongation genes while the D-genome has more fiber initiation genes. Furthermore, there was greater co-linearity among fiber genes in the At and D genomes than between Dt and D chromosome pairs in the tetraploid (AD) cotton genome. These results were unexpected because the D-genome cotton does not produce any spinnable fiber and is the most probable donor of the Dt subgenome. These insights into the evolution of the cotton genomes and the distribution of fiber development genes suggest testable hypotheses about the cotton fiber transcriptome and should guide translational research to exploit genomic regions enhancing fiber yield and quality of cultivated cottons.