Soybean seeds are known to contain high levels of lipoxygenase activity, especially during early stages of germination. Crude mitochondrial fractions from germinating soybeans also have been shown to exhibit high rates of cyanide-insensitive oxygen uptake. These results show the effects of successive discontinuous PercollR density gradients on mitochondrial fractions from 2 day old soybean seeds as judged by polarographic studies and Ouchterlony double diffusion. Axis mitochondria exhibited totally cyanide-sensitive oxygen uptake after two gradients and cotyledon mitochondria exhibited from none to 11% cyanide-insensitive oxygen uptake after three gradients. Mitochondrial fractions which were assayed for lipoxygenase with double diffusion exhibited positive results with fractions that showed cyanide-insensitive oxygen uptake and negative results with cyanide-sensitive mitochondria. These results suggest that lipoxygenase can loosely associate with the mitochondrial membrane and that gradient centrifugation can purify mitochondria free of both lipoxygenase and cyanide-insensitive oxygen uptake.

Typescript (Photocopy) Bibliography: leaves i-xii. (3rd paging sequence)

Thesis (Ph. D.)--University of Adelaide, 1990. / Typescript (Photocopy). Includes bibliographical references (leaves i-xii. (3rd paging sequence)).

No description available.

RNA b is the most abundant member of a family of autonomously replicating single- and double-stranded RNA plasmids found in mitochondria of several maize races. The extent to which this molecule associates in vivo with proteins was investigated by both rate zonal and CsCl equilibrium density gradient centrifugations of clarified lysate of mitochondria from maize plants with the S-type cytoplasm. A soluble endogenous complex of RNA b, responsible for synthesis of the more abundant (+) RNA b strand in in vitro conditions (in mitochondrial lysate), was identified. The complex had a density of 1.49 g/cm$ sp3$ but a surprisingly low sedimentation coefficient, only slightly larger than the naked RNA b. Only a minor fraction of RNA b molecules were bound in the complex; the majority of RNA b sedimented as naked RNA molecules. Complexes synthesizing other, less abundant, maize RNA plasmids were not identified. However, in vitro synthesis of all RNA plasmid species in mitochondrial lysate was resistant to heparin, suggesting that in all cases preformed RdRp-RNA template complexes, capable of elongating in vivo preinitiated RNA plasmid strands, were present.

The structure of one member of a family of maize mitochondrial RNA replicons (or RNA plasmids), RNA b, has been characterized. It is shown that RNA b shares a 13 nucleotide sequence with the central conserved region of Cadang-Cadang viroid of coconuts which might be involved in substrate recognition by the RNA replicase during replication. RNA b likely was derived from a larger member in that family, RNA a, through co-linear deletions similar to those involved with the generation of the defective interfering (DI) elements associated with both animal and plant viruses. RNA b may represent a "selfish" RNA optimized for replication as it does not have the capacity to encode its own replicase. Mitochondrial RNA plasmids have been found not to be restricted to the S and RU cytoplasms, as previously reported. Related plasmid RNAs have been detected in maize plants with C, N and T cytoplasms as well as 13 Latin American races. They were not found, however, in teosintes, indicating that the ancestral nucleic acid from which these RNAs evolved was acquired soon after the split between teosintes and maize, before the divergence of the maize races. Distribution of the plasmid RNAs, a maize mRNA (atp6), and a mitochondrial rRNA (26S) in different organs and tissues was investigated by in situ hybridization. These results indicated that mitochondrial gene expression is subjected to an unexpected degree of both spatial and developmental regulation, and that individual mitochondrial genes are subjected to different controls. Similar results were obtained in in situ hybridization studies of Brassica floral buds. Both studies suggested that the levels of mitochondrial genes transcripts are not particularly high in the tapetal cells of both maize and Brassica anthers contrary to common belief. High levels of RNA plasmid were detected in the pollen of S maize anthers prior to pollen abortion, suggesting they might be related to the cytoplasmic male sterility (CMS) trait of S maize

No description available.

Thesis (M.S.)--Brigham Young University. Dept. of Microbiology and Molecular Biology, 2005. / Includes bibliographical references (p. 56-64).

No description available.

No description available.