Amplification of Nicotiana sylvestris mitochondrial subgenomes is under nuclear control and is associated with phenotypic changes.
We have previously shown the presence in a Nicotiana sylvestris protoplast-derived plant of both a nuclear mutation conferring male sterility (ms4) and a mtDNA reorganisation, named U, characterised by the amplification of substoichiometric mtDNA fragments generated by recombination in the parent T mtDNA. Here we show by physical mapping that the recombining repeats are in direct orientation, thus generating two subgenomes both of which are amplified in the U organisation to the detriment of the parent molecule, and are maintained through sexual reproduction. The nuclear ms4 mutation is likely to have play a role in the shift in mitochondrial molecule equilibrium, as higher levels of recombinant fragments were present in protoplast-derived T calli carrying the ms4 allele than in wild type calli or leaves. The MS4 gene could then lead to conflictual situation. However, subgenomic molecules were counter-selected during the regeneration process, suggesting the existence of different selective pressures in differentiated and non-differentiated cells. The U organisation is associated with higher stem height and late flowering, characters that may not be neutral from a selection point of view. The U equilibrium is an unusual example of sudden mtDNA reorganisation, without obvious differences in genetic information and with only a limited phenotypic impact.
Albert
Béatrice
B
Institut de Biologie Moléculaire des Plantes, CNRS UMR 8618, Bâtiment 630, Université Paris-Sud, 91405 Orsay Cedex, France. beatrice.albert@ese.u-psud.fr
Lelandais
Christine
C
Pla
Magali
M
Leuret
Corine
C
Vitart
Véronique
V
Mathieu
Chantal
C
Sihachakr
Darasinh
D
Godelle
Bernard
B
De Paepe
Rosine
R
D002467:Cell Nucleus; D004272:DNA, Mitochondrial / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics*; D019143:Evolution, Molecular; D005784:Gene Amplification / Q000235:genetics*; D010641:Phenotype; D011995:Recombination, Genetic; D015183:Restriction Mapping; D014026:Nicotiana / Q000235:genetics*
D004272:DNA, Mitochondrial; D018744:DNA, Plant