Mosaic (MSC) cucumbers regenerated from independent cell cultures possess different mitochondrial rearrangements

Abstract

Passage of the highly inbred cucumber ( Cucumis sativus L.) line B through cell culture produces progenies with paternally transmitted, mosaic (MSC) phenotypes. Because the mitochondrial genome of cucumber shows paternal transmission, we evaluated for structural polymorphisms by hybridizing cosmids spanning the entire mitochondrial genome of Arabidopsis thaliana L. to DNA-gel blots of four independently generated MSC and four wild-type cucumbers. Polymorphisms were identified by cosmids carrying rrn18, nad5-exon2, rpl5, and the previously described JLV5 deletion. Polymorphisms revealed by rrn18 and nad5-exon2 were due to one rearrangement bringing together these two coding regions. The polymorphism revealed by rpl5 was unique to MSC16 and was due to rearrangement(s) placing the rpl5 region next to the forward junction of the JLV5 deletion. The rearrangement near rpl5 existed as a sublimon in wild-type inbred B, but was not detected in the cultivar Calypso. Although RNA-gel blots revealed reduced transcription of rpl5 in MSC16 relative to wild-type cucumber, Western analyses revealed no differences for the RPL5 protein and the genetic basis of the MSC16 phenotype remains enigmatic. We evaluated 17 MSC and wild-type lines regenerated from independent cell-culture experiments for these structural polymorphisms and identified eight different patterns, indicating that the passage of cucumber through cell culture may be a unique mechanism to induce or select for novel rearrangements affecting mitochondrial gene expression.

The selection of mosaic (MSC) phenotype after passage of cucumber (Cucumis sativus L.) through cell culture — a method to obtain plant mitochondrial mutants

“…Occasionally, the polymorphic mitochondrial DNAs are the result of the amplification of substoichiometric molecules already present in the mitochondria before passage through cell cultures or are the result of de novo rearrangements during culture after recombination among homologous sequences. Mitochondrial DNA rearrangements in plants usually consist of deletions of coding regions (Lelandais et al 1998) or complex duplications and/or deletions of non-coding mitochondrial DNA regions Bartoszewski et al 2004b).…”

“…The mitochondrial genome of cucumber shows paternal transmission and there are no reports of variation for mitochondrial DNA transmission in cucumber, such as an occasional maternal transmission (Havey et al 2004). The mitochondrial DNA of MSC lines was heterogeneous and approximately one wild-type genome was found for every 500 genomes carrying the JLV5 deletion as detected by PCR ) and wild-type progeny scoring (Bartoszewski et al 2004b). Sequence analyses revealed that the JLV5 deletion was not a single event and was part of a complex rearrangement involving mitochondrial regions carrying rpl5 and JLV5 (Bartoszewski et al 2004b).…”

“…The MSC phenotype shows paternal inheritance (Malepszy et al 1996), indicating that MSC is conditioned by the mitochondrial DNA. Detailed studies of MSC lines showed that they possess complex rearrangements in the mitochondrial genome Bartoszewski et al 2004b).…”

Plasma membrane-generated ROS and their possible contribution to leaf cell growth of cucumber (Cucumis sativus) MSC16 mitochondrial mutant

“…Crossing the MSC16 mutant with line B showed that the MSC16 phenotype is not associated with either the nuclear or the chloroplast genome (Malepszy et al 1996). Plants with the MSC16 phenotype have a JLV5 deletion in a non-coding region of the mitochondrial genome, although the precise nature of this mutation remains unknown (Bartoszewski et al 2004). The MSC16 line has marked phenotypic changes, including a slower growth rate and a leaf mosaic pattern with chlorotic patches (Malepszy et al 1996).…”

Origin of the CMS gene locus in rapeseed cybrid mitochondria: Active and inactive recombination produces the complex CMS gene region in the mitochondrial genomes of Brassicaceae

“…In many instances, recombination and the resulting substoichiometric shifting (changes in the relative levels of molecules) were observed in cell culture and in regenerated plants (Hartmann et al, 1992;Kanazawa et al, 1994;Bartoszewski et al, 2004). Mackenzie and colleagues revealed that Msh1, a gene involved in the suppression of mitochondrial DNA rearrangements, appeared to be involved in the suppression of illegitimate recombination in plant mitochondria (Abdelnoor et al, 2003(Abdelnoor et al, , 2006.…”