Cool as the Cucumber Mitochondrial Genome: Complete Sequencing Reveals Dynamics of Recombination, Sequence Transfer, and Multichromosomal Structure

Abstract

Schematic of the cucumber mitochondrial genome. The large (1556 kb) and two small (84 and 45 kb) circular-mapping chromosomes of the cucumber mitochondrial genome. Genes and introns are shown in green, foreign DNA in red, and sequences shared with the nuclear genome in blue. The gray lines connect large recombining repeats. (Figure courtesy of A .J. Alverson.) www.plantcell.org/cgi

Moramonas marocensis gen. nov., sp. nov.: a jakobid flagellate isolated from desert soil with a bacteria-like, but bloated mitochondrial genome

“…The unusually large genome size of the M. marocensis mitochondrion appears to be a relatively recent change from a more canonical, gene-dense form since M. marocensis is phylogenetically nested within a clade that shares this overall form. Whether this bloating is due to similar causes to that of the land plant mitochondria remains unclear at this point, but there is no evidence for excessive repetitive sequences or repeat-mediated recombination, as known for some plant mitochondrial genomes [ 45 , 46 ], and no evidence for an invasion of detectably extra-organellar DNA. Whether the mitochondrion of M. marocensis consists of several or only one circular (most jakobids [ 18 ]) or linear ( Jakboa libera [ 18 ]) chromosome is also not clear.…”

Gene Arrangement Convergence, Diverse Intron Content, and Genetic Code Modifications in Mitochondrial Genomes of Sphaeropleales (Chlorophyta)

“…Land plant mt genomes are known for their great size variation, horizontal gene transfer, and frequent rearrangements (e.g., Palmer and Herbon 1988 ; Adams et al 2002 ; Mach 2011 ). Their coding regions generally maintain their integrity, although sometimes they are transferred to the nucleus.…”

Structural variations in plant genomes

“…Several studies have reported the presence of subgenomic structural variations in mitochondrial genomes that have arisen from inversions and translocations [ 56 , 57 ]. While such events in plant mitochondria increase organelle genome complexity, recombination has also been found to maintain genomic stability and may provide a mechanism to increase genetic variation in the absence of sexual reproduction [ 58 ]. Genomic inversions can be a driver of speciation, and this has been studied in plants using comparative genomics [ 59 , 60 ].…”