A variant mitochondrial DNA arrangement specific toPetunia stable sterile somatic hybrids

Abstract

We have characterized two related regions of twoPetunia mitochondrial genomes in order to understand how plant mt genomes from a cytoplasmic male sterile (cms) line and a fertile line diverge from one another. Restriction maps of these regions indicate that a sequence arrangement shared by the two genomes adjoins sequences which are not shared at the corresponding locations in the two genomes. A point where the mt genomes from the cms line and the fertile lines diverge from each other was identified and mapped.Previously we had observed that somatic hybrids constructed from the cms and the fertile line contained mt genomes carrying new combinations of parental mtDNA restriction fragments (3). Using the restriction maps of the two related mtDNA regions, a mtDNA arrangement unique to the cms parent could be shown to be present in all 17 stable sterile somatic hybrids tested and none of the 24 stable fertile somatic hybrids tested. This data does not exclude the possibility that additional, as yet unidentified, mtDNA arrangements unique to the cms parent might also be found exclusively in sterile somatic hybrids. Whether or not the sterile parental mtDNA arrangement reported here is functionally related to cms, it apparently segregates with cms in somatic hybrids.

Interactions of Mitochondrial and Nuclear Genes That Affect Male Gametophyte Development

“…In Petunia, a restriction fragment length polymorphism was identified that segregated with CMS in somatic hybrids containing recombinant mtDNAs (Boeshore et al, 1985), leading to the finding of a CMS-associated locus containing the so-called pcf (petunia CMS-associated fused) gene (Figure 1), which is composed of portions of the coding regions of atp9, cox2, and an unidentified reading frame termed urfS (Young and Hanson, 1987). The locus also contains the normal copies of the nad3 and rps12 genes as well as nine codons evidently derived from an unidentified gene, orf143, found in fertile petunia lines (Hanson et al, 1999).…”

Fertility Restoration Is Associated with Loss of a Portion of the Mitochondrial Genome in Cytoplasmic Male-Sterile Common Bean.

“…The study of CMS has raised a number of interesting and, as yet, unanswered questions regarding the role of nuclear-cytoplasmic gene interaction in plant development. Although a number of investigators have demonstrated an association between the CMS phenotype and the mitochondrial genome (Warmke and Lee, 1977;Forde and Leaver, 1980;Boeshore et al, 1985;Schardl et al, 1985;Wise et al, 1987), the cause of pollen abortion remains to be determined. In most cases of CMS in higher plants, pollen viability can be restored by the introduction of a nuclear fertility restorer gene that appears to mask expression of the CMS trait.…”

Identification of a mitochondrial protein associated with cytoplasmic male sterility in petunia.

“…Presumably, some defect in mitochondrial function results in the arrest of normal pollen development observed in sterile genotypes. Although mitochondrial DNA regions correlated with CMS have been identified in petunia (Boeshore, Hanson, and Izhar, 1985;Young and Hanson, 1987) and maize (Dewey, Levings, and Timothy, 1986), their role in producing the sterility phenotype is not understood. The petunia and maize CMSassociated regions do not share sequence homology (Hanson, Pruitt, and Nivison, 1989).…”

“…The recombinant mitochondrial genomes made it possible to search for a mitochondrial DNA region that segregated with sterility in the somatic hybrids. Such a region was found (Boeshore et al, 1985) and named the S-pcf locus . Sequenc-' To whom correspondence should be addressed.…”