Mechanism Of Cytoplasmic Male Sterility Research Articles

On the mechanism of cytoplasmic male sterility in the 447 line of Vicia faba

The trait of cytoplasmic male sterility, expressed in plants bearing the 447 cytoplasm of Vicia faba, is uniquely and positively correlated with the presence of a linear double-stranded RNA molecule (dsRNA) 16.7 kb in size. Restriction enzyme digestion profiles of mitochondrial DNA isolated from fertile and cytoplasmic malesterile (CMS) lines do show a limited number of specific differences in fragment intensities and mobilities. However, mitochondria isolated from the progeny of the cross CMS × Restorer line contain DNA with an identical restriction profile as the male-sterile parent: moreover, subsequent generations are completely and permanently fertile, even upon segregation of the nuclear restoration gene. Southern hybridizations, using cDNA clones as probes, reveal homology between the CMS-associated dsRNA and the nuclear genome of both sterile and fertile lines. The regions cloned, representing approximately 22% of the total dsRNA sequence, show no homology to organelle DNA. We have not been able to stably transmit the dsRNA to fertile lines of V. faba or any other plant species, using a variety of standard virological techniques.

日本稲における雄性不稔細胞質及び正常細胞質由来のミトコンドリアDNAの差異

We attempted to analyse the mechanism of cytoplasmic male sterility (cms) in two strains of rice, that is, cms-Bo Taichung 65 with cytoplasm of cultivar Chinsurah Boro II and cms-R Reimei with cytoplasm of a strain of Oryza rufipogon. Mitochondrial DNAs (mtDNAs) were purified from cms and fertile (normal) rice varieties and the electrophoretic pattern of their restriction fragments was compared. MtDNA purified from cultivar Chinsurah Boro II cytoplasm contained two plasmid-like low molecular weight DNAS and the pattern of the restriction fragments of mtDNA from Chinsurah Boro II cytoplasm was clearly different from that of the normal cytoplasm. Plasmid-like DNAs have not been detected yet in the mtDNA from a strain of Oryza rufipogon cytoplasm but the pattern of the restriction fragments of mtDNA was also obviously different from that of the normal cytoplasm. Moreover the pattern of the restriction fragments of mtDNAS from a strain of Oryza rufipogon and Chinsurah Boro II cytoplasms was clearly different. In contrast, the pattern of the restriction fragments of chloroplast DNAS from normal and cms cytoplasms of Taichung 65 or Reimei was identical. We speculate that the difference in the mitochondrial genome between cms and normal 'cytoplasms of Taichung 65 or Reimei is, at least partly, responsible for the occurrence of cms.

Microsporogenesis and the Mechanism of Cytoplasmic Male Sterility in Maize

Examination of the structural changes occurring during microsporogenesis in cms-T, -C and -S Zea mays L. with different nuclear backgrounds revealed considerable variations in the stages at which abortion of the sporocytes occurred within each cytoplasmic genotype. This variation was not associated with the nuclear background. Significantly, we found that the mitochondria in cms-T plants did not always follow the pattern of degeneration described previously. We conclude that these observations are not consistent with a proposed mechanism of cytoplasmic male sterility involving the direct, antagonistic action of an anther produced substance on an altered mitochondrion or plastid, that is functionally normal in the rest of the plant. The value of microscopic studies in detecting variation in apparently uniform material is emphasised, though it is recognized that other methods will be required to elucidate the mechanism of male sterility.

Nature and Mechanisms of Cytoplasmic Male Sterility in Plants: a Review1

Abstract Cytoplasmic male sterility (CMS) has been described in many of our cultivated crops and is commercially useful in the production of hybrids when pollen vectors will provide the necessary economic levels of seed production. In the more common type, the sporophytic, the development of the microspore is affected by the abnormal growth of the tapetum or mistiming of callose formation and, in corn at least, the mitochondrial complex is involved. In the gametophytic system the factor causing abortion of the pollen apparently resides in the microspore rather than in its environment. Other systems which suggest plasmid-like inclusions associated with CMS have been reported. Transfer to the cytosterile mechanism by cell fusion has been accomplished, but wider application of this technique waits on methods for development of plants from naked protoplasts In more species.

Possible mitochondrial involvement in mechanism of cytoplasmic male sterility in maize (Zea mays L.)

The mechanism of cytoplasmic male sterility was investigated in maize by isolating mitochondria from seedlings and various anther stages and analyzing cytochrome oxidase and succinic dehydrogenase biochemically and electrophoretically. Sterile anthers exhibited a lack of biochemical activity and fewer isozymatic bands for cytochrome oxidase. No apparent differences were detected biochemically or electrophoretically between fertile and sterile anthers for succinate dehydrogenase.

A model for the mechanism of cytoplasmic male sterility in plants, with special reference to maize

A model is proposed to account for the features of cytoplasmically inherited male sterility in higher plants. It is suggested that normal anther development is prevented by an interaction between a substance(s) present only in anthers and organelles with altered structures. The alterations in the organelles (mitochondria or chloroplasts) result from mutations in mitochondrial or chloroplast DNA. The involvement of a regulatory substance(s) under developmental control can account for the variation in the extent of sterility in different anthers and the dependence of sterility on the environment. Nuclear fertility restorer genes are postulated to correct the altered organelle structure making the organelles insensitive to the anther substance(s) or to interfere with the production or transport of the anther substance(s). The model, which can be experimentally tested, has been derived from observations that somatic maize mitochondria from certain cytoplasmic male sterile genotypes have altered structures and these altered structures are partially reverted in the presence of nuclear fertility restorer alleles.