Analysis of the Complete Mitochondrial Genome Sequence of the Diploid Cotton<i>Gossypium raimondii</i>by Comparative Genomics Approaches

Abstract

Cotton is one of the most important economic crops and the primary source of natural fiber and is an important protein source for animal feed. The complete nuclear and chloroplast (cp) genome sequences of <i>G. raimondii</i> are already available but not mitochondria. Here, we assembled the complete mitochondrial (mt) DNA sequence of <i>G. raimondii</i> into a circular genome of length of 676,078 bp and performed comparative analyses with other higher plants. The genome contains 39 protein-coding genes, 6 rRNA genes, and 25 tRNA genes. We also identified four larger repeats (63.9 kb, 10.6 kb, 9.1 kb, and 2.5 kb) in this mt genome, which may be active in intramolecular recombination in the evolution of cotton. Strikingly, nearly all of the <i>G. raimondii</i> mt genome has been transferred to nucleus on Chr1, and the transfer event must be very recent. Phylogenetic analysis reveals that <i>G. raimondii</i>, as a member of Malvaceae, is much closer to another cotton (<i>G. barbadense</i>) than other rosids, and the clade formed by two <i>Gossypium</i> species is sister to Brassicales. The <i>G. raimondii</i> mt genome may provide a crucial foundation for evolutionary analysis, molecular biology, and cytoplasmic male sterility in cotton and other higher plants.