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  • 1
    ISSN: 1432-2242
    Keywords: Electric field-induced microfusion ; Microculture ; Nicotiana ; Somatic hybridization ; Cytoplasmic male sterility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Somatic hybrid/cybrid plants were obtained by microfusion of defined protoplast pairs from malefertile, streptomycin-resistant Nicotiana tabacum and cytoplasmic male-sterile (cms), streptomycin-sensitive N. tabacum cms (N. bigelovii) after microculture of recovered fusants. Genetic and molecular characterization of the organelle composition of 30 somatic hybrid/cybrid plants was performed. The fate of chloroplasts was assessed by an in vivo assay for streptomycin resistance/ sensitivity using leaf explants (R0 generation and R1 seedlings). For the analysis of the mitochondrial (mt) DNA, species-specific patterns were generated by Southern hybridization of restriction endonuclease digests of total DNA and mtDNA, with three DNA probes of N. sylvestris mitochondrial origin. In addition, detailed histological and scanning electron microscopy studies on flower ontogeny were performed for representative somatic hybrids/cybrids showing interesting flower morphology. The present study demonstrates that electrofusion of individually selected pairs of protoplasts (microfusion) can be used for the controlled somatic hybridization of higher plants.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2145
    Keywords: Nicotiana ; Cytoplasmic male sterility ; Flower morphogenesis ; mtDNA organization ; In organello protein synthesis ; Mitochondrial transcripts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A detailed description of in planta floral ontogeny based on scanning electron microscopy, developmental histology and morphology is presented for three different alloplasmic gene-cytoplasmic male-sterile (CMS)Nicotiana tabacum isonuclear lines with cytoplasms ofN. bigelovii, N. debneyi and N. suaveolens and compared to the corresponding nuclear donorN. tabacum genotype. This allowed the precise determination of the developmental stages affected in the mutant forms as well as a thorough phenotypic characterization of them. The organization of the mitochondrial genome and expression of mitochondrial DNA (mtDNA) was investigated in the three different alloplasmic CMS tobacco analogs and compared to the corresponding malefertile parentalNicotiana species. Southern hybridizations of total cellular DNA and mtDNA from the different sets of lines with probes specific for mitochondrial genes coding for cytochrome oxidase subunits I, II and III, apocytochrome b, ATPase subunits α and 9 as well as 18S-5S ribosomal RNA indicated that: (a) mtDNA organization is different between mitochondrial genomes of fertile and sterile lines but identical in two different fertile tobacco lines; however genetic similarity among different mitochondrial genome types can be revealed by restriction fragment patterns; (b) although several differences were detected between the male-sterile and male-fertile plants, most of these were related to the origin of the mitochondria (cytoplasm donorNicotiana species); (c) identical mtDNA rearrangements — distinct to the cytoplasm donor — occur in cytoplasmic malesterile tobacco analogs bearing cytoplasm fromN. bigelovii in two differentN. tabacum nuclear backgrounds, indicating that mitochondrial genome structure inNicotiana is altered by substitution of the nuclear back-ground, since (d) inter- and intraspecific mitochondrial genome diversity among differentNicotiana species and the corresponding alloplasmic CMS tobacco analogs can be determined by hybridization with mtDNA specific probes. Analysis of in organello translation products in the three CMS-systems described confirmed the presence of variant proteins synthesized by mitochondria from CMS and male-fertileNicotiana isonuclear lines. In addition, differences due to the origin of both the nucleus and the cytoplasm, which involve changes in the presence or size of particular polypeptides, are apparent. A common feature of all three systems — including two different nuclear backgrounds — is the enhanced synthesis of a 31-kDa polypeptide in the strictly isonuclear CMS lines compared to the male-fertile tobacco. In addition, organellar gene expression was studied by Northern blot analysis of transcripts homologous to mitochondrial gene probes, revealing variant mtRNA species associated with some CMS lines.
    Type of Medium: Electronic Resource
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