THE PLANT CELL, Vol 3, Issue 8 759-769, Copyright © 1991 by American Society of Plant Biologists
Modifications of Mitochondrial DNA Cause Changes in Floral Development in Homeotic-like Mutants of Tobacco
W. Kofer, K. Glimelius and H. T. Bonnett
Department of Plant Breeding, Swedish University of Agricultural Sciences, S-75007 Uppsala, Sweden
To investigate the influence of mitochondrial genes on stamen development
of higher plants, protoplasts from three different, male-sterile tobacco
cultivars were fused. The fused cells were cultured individually into
calli, from which plants were regenerated. Cybrid plants were obtained that
exhibited flowers with recombined biparental male-sterile morphology and
with novel male-sterile stamens that differed from any types from sexual or
somatic hybridizations described previously. The male-sterile morphologies
of these cybrids and their parents support the hypothesis that
nuclear-mitochondrial interaction occurs at several stages in tobacco
floral development and that several mitochondrial genes are necessary for
normal stamen and corolla development. Analysis by restriction endonuclease
digestion of mitochondrial DNA of male-sterile cybrids and their parents
revealed that the mitochondrial DNA of male-sterile cybrids with parental
floral morphology was unchanged when compared with parental mitochondrial
DNA. Cybrids that were morphologically similar to one parent's male-sterile
phenotype had mitochondrial DNA almost identical to that parent, whereas
cybrids with recombined biparental or novel male-sterile phenotypes
contained mitochondrial DNA different from both male-sterile parents and
from each other. A set of mitochondrial DNA fragments could be correlated
with split corollas, a feature found in several tobacco male-sterile
cultivars. DNA gel blot analysis using a number of mitochondrial genes
confirmed the conclusions based on ethidium bromide staining of
mitochondrial DNA restriction digests.
