Accumulation of Large Lineage-Specific Repeats Coincides with Sequence Acceleration and Structural Rearrangement in Plantago Plastomes.

Repeats can mediate rearrangements and recombination in plant mitochondrial genomes and plastid genomes. While repeat accumulations are linked to heightened evolutionary rates and complex structures in specific lineages, debates persist regarding the extent of their influence on sequence and structural evolution. In this study, 75 Plantago plastomes were analyzed to investigate the relationships between repeats, nucleotide substitution rates, and structural variations.

Leaf variegation caused by plastome structural variation: an example from .

Variegated plants often exhibit plastomic heteroplasmy due to single-nucleotide mutations or small insertions/deletions in their albino sectors. Here, however, we identified a plastome structural variation in albino sectors of the variegated plant (Asphodelaceae), a perennial herbaceous plant widely cultivated as an ornamental in tropical Asia. This structural variation, caused by intermolecular recombination mediated by an 11-bp inverted repeat flanking a 92-bp segment in the large single-copy region (LSC), generates a giant plastome (228 878 bp) with the largest inverted repeat of 105 226 bp and the smallest LSC of 92 bp known in land plants.

Genome copy number predicts extreme evolutionary rate variation in plant mitochondrial DNA.

Nuclear and organellar genomes can evolve at vastly different rates despite occupying the same cell. In most bilaterian animals, mitochondrial DNA (mtDNA) evolves faster than nuclear DNA, whereas this trend is generally reversed in plants. However, in some exceptional angiosperm clades, mtDNA substitution rates have increased up to 5,000-fold compared with closely related lineages.