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Biology Articles » Botany » The Elusive Plant Mitochondrion as a Genetic System » Study of mitochondrial genetics

Study of mitochondrial genetics
- The Elusive Plant Mitochondrion as a Genetic System


Many of the most important lessons regarding mitochondrial function have been leamed through investigations in fungal systems, most notably yeast (Saccharomyces cerevisiae). This is primarily because the indispensable nature of mitochondrial functions to the higher eukaryotic cell makes mutational analysis in studies of mitochondrial genetics generally infeasible. In those yeasts that are able to survive without a functional mitochondrion via fermentation, a large collection of important mutations in mitochondrial genes as well as nuclear genes involved in mitochondrial functions is available. This collection, together with the availability of nuclear gene disruption and replacement technologies and DNA mediated mitochondrial transformation systems, has allowed the elucidation of a number of important mitochondrial processes in biogenesis and gene expression (Bolotin-Fukuhara and Grivell, 1992). It has, as well, facilitated the identification of both mitochondrial and nuclear genes involved in mitochondrial function in higher eukaryotes, including plants.

Many more difficulties arise in the direct identification of genetic components of the nuclear-mitochondrial communication network in higher-plant systems. Gene mutations that interfere with normal mitochondrial function are likely to be lethal and can be maintained only in a heteroplasmic (mixed mitochondrial) population. The nonchromosomal stripe mutants of maize represent mutations within essential mitochondrial genes maintained via heteroplasmy and observed as sectoring within the plant (Gu et al., 1993). Mitochondrial genomic alterations have been associated with enhanced disease susceptibility (Levings, 1993), altered chloroplast function (Roussell et al., 1991; Martinez-Zapater et al., 1992), severe growth abnormalities (Newton et al., 1989), reduced plant vigor (Jan, 1992), and aberrant floral developmental patterns (Kofer et al., 1991; Gourret et al., 1992). Additionally, a large collection of plant mitochondrial mutations that result in abnormal pollen development, known as cms, has accumulated over the past 20 years. The phenomenon of cms, reported in over 150 plant species, has provided an important focus for studies of mitochondrial genomic alteration, gene expression, and nuclear-mitochondrial genetic interactions.

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