A major deletion in the cucumber mitochondrial genome sorts with the MSC phenotype

Abstract

The cucumber mitochondrial genome is unique because of its large size, paternal transmission, and the existence of a paternally transmitted mosaic (MSC) phenotype spontaneously appearing after independent tissue culture experiments. Transmission studies eliminated paternal imprinting as the genetic basis for the MSC phenotype. We identified a 13 kb region (JLV5-DEL) in the wild-type mitochondrial genome that was absent from three MSC lines. This deleted region was paternally transmitted with the MSC phenotype through the F3 and test-cross generations. Southern hybridizations and PCR amplifications using primers within the JLV5 region revealed that rare wild-type sorters possessed the wild-type region. MSC plants possess the wild-type region at levels (approximately 0.002) below detection by standard PCR reactions and Southern hybridizations, using genomic DNA. Sequence analysis of the wild-type contig revealed no homologies to mitochondrial genes and no open reading frames within JLV5-DEL. PCR amplifications across JLV5-DEL using MSC mtDNA revealed that the loss of this region was not a simple deletion and may be associated with a rearrangement. Because no genic regions were identified within the wild-type JLV5 region, the specific lesion conditioning the MSC phenotype may be associated with the putative rearrangement or another mutation that occurred during tissue culture or exists substoichiometrically in the parental line and is transmitted together with JLV5 within the same mitochondrion.

Counting mtDNA molecules in Phaseolus vulgaris: sublimons are constantly produced by recombination via short repeats and undergo rigorous selection during substoichiometric shifting

“…Precise quantification of these molecules was rarely reported (Arrieta-Montiel et al 2001;Laser et al 1997;Lilly et al 2001;Welch et al 2006) and only two reports were based on real-time PCR (Arrieta-Montiel et al 2001;Welch et al 2006). Sublimons' quantities, estimated relative to the main genome, varied from 10 -6 to 10 -3 .…”

Changes in energy status of leaf cells as a consequence of mitochondrial genome rearrangement

“…MSC16 line possesses large deletion in its mitochondrial genome (named JLV5) but in this area no open reading frame was found. Moreover, reduced amount of rpl5 transcripts was found in MSC16 line but at the protein level, no diVerences between MSC16 and WTc line was observed (Lilly et al 2001;Bartoszewski et al 2004). Although the genetic basis of this mutation remains enigmatic, biochemical studies indicated that mitochondrial mutation aVects mitochondrial respiratory activity.…”

“…Because of this, mitochondrially encoded traits can be easily separated from traits conditioned by the chloroplast genome. All crosses, backcrosses, and self-pollinations of the wild type by MSC16 plants showed paternal transmission (Malepszy et al 1996), and imprinting of paternal nuclear alleles was eliminated (Lilly et al 2001;Bartoszewski et al 2004). MSC16 line possesses large deletion in its mitochondrial genome (named JLV5) but in this area no open reading frame was found.…”

Mitochondrial mutant MSC cucumber shows impaired somatic

“…MSC plants appear at different frequencies in different types of cell cultures (Burza and Malepszy, 1995;Łady_ zy nski et al, 2002). The plants are not identical genetically as they show different rearrangements in the mitochondrial genome (Lilly et al, 2001;Bartoszewski et al, 2004). These data indicate that passage of cucumber through cell cultures and regeneration of the plants can be a method to induce or select for unique rearrangements affecting mitochondrial gene expression (Bartoszewski et al, 2004).…”

“…MSC16 is one of the MSC lines and it is associated with complex mitochondrial rearrangements causing DNA deletions and duplications (Lilly et al, 2001;Bartoszewski et al, 2004). The rearranged molecule(s) exists as a sublimon(s) in inbred line B and becomes predominant in MSC16.…”