Phylogenetic analysis of mitochondrial mutation rate variation in the angiosperm tribe Sileneae

• Background: Recent phylogenetic studies have revealed that the   mitochondrial genome of the angiosperm Silene noctiflora   (Caryophyllaceae) has experienced a massive mutation-driven   acceleration in substitution rate, placing it among the fastest   evolving eukaryotic genomes ever identified. To date, it appears that   other species within Silene have maintained more typical substitution   rates, suggesting that the acceleration in S. noctiflora is a recent   and isolated evolutionary event. This assessment, however, is based on   a very limited sampling of taxa within this diverse genus.   Results: We analyzed the substitution rates in 4 mitochondrial genes   (atp1, atp9, cox3 and nad9) across a broad sample of 74 species within   Silene and related genera in the tribe Sileneae. We found that S.   noctiflora shares its history of elevated mitochondrial substitution   rate with the closely related species S. turkestanica. Another section   of the genus (Conoimorpha) has experienced an acceleration of   comparable magnitude. The phylogenetic data remain ambiguous as to   whether the accelerations in these two clades represent independent   evolutionary events or a single ancestral change. Rate variation among   genes was equally dramatic. Most of the genus exhibited elevated rates   for atp9 such that the average tree-wide substitution rate for this   gene approached the values for the fastest evolving branches in the   other three genes. In addition, some species exhibited major   accelerations in atp1 and/or cox3 with no correlated change in other   genes. Rates of nonsynonymous substitution did not increase   proportionally with synonymous rates but instead remained low and   relatively invariant.   Conclusion: The patterns of phylogenetic divergence within Sileneae   suggest enormous variability in plant mitochondrial mutation rates and   reveal a complex interaction of gene and species effects. The variation   in rates across genomic and phylogenetic scales raises questions about   the mechanisms responsible for the evolution of mutation rates in plant   mitochondrial genomes.

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NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

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Biology

Biologi

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