Diversity of Vicia faba circular mtDNA in whole plants and suspension cultures

Abstract

A comparative analysis of the Vicia faba mitochondrial genome in whole plants and in longterm suspension culture has been conducted. Restriction fragment patterns of the mtDNA isolated from these two sources were notably different. Electronmicroscopic analysis also revealed significant differences. Large circular mtDNA patterns shifted from a 37-80 kb subpopulation, which was predominant in whole plants, to 18-34 kb subpopulations although in both classes notable quantities of circular molecules of 80 to 120 kb and more were also found. Both in whole plant and suspension culture cells very large circular DNAs were observed. Some of them had lengths nearly 290 kb and could be considered as evidence of the existence of master chromosomes. The minicircular DNA population was also altered. In the suspension culture we observed a notable increase of percentage of minicircles with sizes near 1 kb. Simultaneously, the percentage of minicircles with sizes near 3.5-10 kb significantly increased in suspension culture cells. In addition, a new peak (10-12 kb) of minicircles appeared. Copy number alterations for some sequences homologous to CCC1A, CCC1B and CCC2 (Negruk et al. 1982, 1985) were shown. Southern hybridization revealed the existence of a family of minicircles having sizes 1.4-2 kb with predominance of CCC1A, CCC1B and CCC2. The copy numbers of CCC1B and some minor minicircles was changed in the suspension culture when compared with the whole plants.

Patterns of mitochondrial DNA instability in Brassica campestris cultured cells

“…Third, both in our evolutionary and in vitro studies we noted that most of the structural alterations of the Brassica mitochondrial genome occur at specific sites via recombination across short repeated elements. Although a number of studies have already demonstrated an increased plasticity of plant mtDNA in response to tissue culture manipulations [ 17,7,39,41,50,21,4] it is still uncertain as to whether these 'culture-induced' alterations occur systematically in all higher-plant species or whether they reflect particular culture conditions such as culture age [34] or the in vitro technique employed [23]. A study of in vitro mtDNA alterations of maize [7] has also shown that the occurrence of specific types of rearrangements (i.e.…”

“…inversion, deletion/insertion, transposition) in the organization of the mitochondrial genome may be observed [7, 34,62]. The instability of the mitochondrial genome has been investigated in somatic hybrids [ 15,38,60,41,21 ] as well as in vitro cultures of various plant systems [8,39,18,58,50,4]. An often cited example of culture-induced somaclonal variation associated with mtDNA is the reversion to fertility of different cytoplasmic malesterile types in maize [16,5,12,48].…”

Plant mitochondrial DNA

“…In the vast majority of publications mtDNA is observed as a collection of linear molecules in varying sizes (15). In fact, there have only been two instances where circular DNA molecules large enough to be mitochondrial genomes have been observed at very low levels in the lower plant liverwort (28) and in Vicia faba (29).…”

The use of mitochondrial DNA polymorphisms to distinguish commercial cultivars of the broad bean, Vicia faba L.

“…and those that have been initiated were primarily concerned with variation in minicircular mt plasmids or other DNA arrangements associated with tissue culture and cytoplasmic male sterility (Negruk & Kaushik, 1988 ;Negruk et al ., 1986 ;Goblet et al ., 1985) . In addition few successful studies have employed nuclear RFLPs to distinguish cultivars of VV faba (Van de Ven et al ., 1991) and even these studies indicate limited variation.…”