Entire nucleotide sequences of Gossypium raimondii and G.arboreum mitochondrial genomes revealed A-genome species as cytoplasmic donor of the allotetraploid species

Cotton (Gossypium spp.) is commonly grouped into eight diploid genomic groups, designated A-G and K, and an allotetraploid genomic group, AD. Gossypium raimondii (D-5) and G.arboreum (A(2)) are the putative contributors to the progenitor of G.hirsutum (AD(1)), the economically important fibre-producing cotton species. Mitochondrial DNA from week-old etiolated seedlings was extracted from isolated organelles using discontinuous sucrose density gradient method. Mitochondrial genomes were sequenced, assembled, annotated and analysed in orderly. Gossypium raimondii (D-5) and G.arboreum (A(2)) mitochondrial genomes were provided in this study. The mitochondrial genomes of two diploid species harboured circular genome of 643,914bp (D-5) and 687,482bp (A(2)), respectively. They differ in size and number of repeat sequences, both contain illuminating triplicate sequences with 7317 and 10,246bp, respectively, demonstrating dynamic difference and rearranged genome organisations. Comparing the D-5 and A(2) mitogenomes with mitogenomes of tetraploid Gossypium species (AD(1), G.hirsutum; AD(2), G.barbadense), a shared 11kbp fragment loss was detected in allotetraploid species, three regions shared by G.arboreum (A(2)), G.hirsutum (AD(1)) and G.barbadense (AD(2)), while eight regions were specific to G.raimondii (D-5). The presence/absence variations and gene-based phylogeny supported that A-genome is a cytoplasmic donor to the progenitor of allotetraploid species G.hirsutum and G.barbadense. The results present structure variations and phylogeny of Gossypium mitochondrial genome evolution.