Abstract
The significant difference in the mtDNA size and structure with simultaneous slow evolving genes makes the mitochondrial genome paradoxical among all three DNA carriers in the plant cell. Such features make mitochondrial genome investigations of particular interest. The genus Helianthus is a diverse taxonomic group, including at least two economically valuable species—common sunflower (H. annuus) and Jerusalem artichoke (H. tuberosus). The successful investigation of the sunflower nuclear genome provided insights into some genomics aspects and significantly intensified sunflower genetic studies. However, the investigations of organelles’ genetic information in Helianthus, especially devoted to mitochondrial genomics, are presented by limited studies. Using NGS sequencing, we assembled the complete mitochondrial genomes for H. occidentalis (281,175 bp) and H. tuberosus (281,287 bp) in the current investigation. Besides the master circle chromosome, in the case of H. tuberosus, the 1361 bp circular plasmid was identified. The mitochondrial gene content was found to be identical for both sunflower species, counting 32 protein-coding genes, 3 rRNA, 23 tRNA genes, and 18 ORFs. The comparative analysis between perennial sunflowers revealed common and polymorphic SSR and SNPs. Comparison of perennial sunflowers with H. annuus allowed us to establish similar rearrangements in mitogenomes, which have possibly been inherited from a common ancestor after the divergence of annual and perennial sunflower species. It is notable that H. occidentalis and H. tuberosus mitogenomes are much more similar to H. strumosus than H. grosseserratus.
Highlights
In contrast to animals, in which mitochondrial genomes are usually conserved in size and gene content across large taxonomic groups, plant’s mitogenomes display high variability in size and structure, as well as having distinct features even in closely related species [1,2]
The complete master cycle mitochondrial chromosomes were obtained for H. occidentalis (281,175 bp) and H. tuberosus (281,287 bp)
The mitochondrial gene content is identical for both sunflower species, counting 32 protein-coding genes, 3 rRNA, 23 tRNA genes, and 18 open reading frames (ORFs)
Summary
In which mitochondrial genomes are usually conserved in size and gene content across large taxonomic groups, plant’s mitogenomes display high variability in size and structure, as well as having distinct features even in closely related species [1,2]. The angiosperm mitogenome size ranges from 66 kbp in Viscum scurruloideum [3] to 11.3 Mbp in Silene conica [4] Such a difference in higher plant mitochondrial DNA (mtDNA) may be associated with frequent insertions, rapid rearrangements, and complex multipartite structures, often involved in recombination [5]. The significant difference in the mtDNA size and structure with simultaneous slow evolving genes makes the mitochondrial genome paradoxical among all three DNA carriers in the plant cell. Such features make the mitochondrial genome interesting to study [8]
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