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Malate dehydrogenase: viability of cytosolic nulls and lethality of mitochondrial nulls in maize
Abstract:
Five independently inherited loci on five distinct chromosomes encode the mitochondrial and cytosolic isozymes of NAD-dependent malate dehydrogenase (MDH; L-malate:NAD+ oxidoreductase, EC 1.1.1.37). Multiple alleles, including electrophoretic nulls, occur for each locus. However, a single allele of normal activity at one of the three loci encoding the mitochondrial MDHs is sufficient for normal development, whereas plants with essentially no cytosolic MDH activity function normally. The requirement of a normal activity allele at one of the three structural loci encoding the mitochondrial MDHs demonstrates in plants that a commonly studied dehydrogenase enzyme is essential for normal embryogenesis.
Insights
Mitochondrial NAD-dependent malate dehydrogenase (MDH) is essential for plant embryogenesis, as shown by genetic studies. Cytosolic MDH, however, is not required for normal plant development.
Area of Science:
- Plant genetics and molecular biology
- Enzyme function and regulation
- Developmental biology
Background:
- NAD-dependent malate dehydrogenase (MDH) exists as mitochondrial and cytosolic isozymes in plants.
- These isozymes are encoded by multiple independently inherited loci on different chromosomes.
- Understanding the essentiality of specific isozymes is crucial for comprehending plant development.
Purpose of the Study:
- To investigate the essentiality of mitochondrial and cytosolic NAD-dependent malate dehydrogenase (MDH) isozymes for plant development.
- To determine the genetic basis and allelic variation of MDH isozymes.
- To establish the role of MDH in plant embryogenesis.
Main Methods:
- Genetic analysis of five independently inherited loci encoding MDH isozymes.
- Characterization of multiple alleles, including electrophoretic nulls, for each locus.
- Assessment of plant development and embryogenesis in relation to MDH activity.
Main Results:
- Plants possess multiple loci for mitochondrial and cytosolic NAD-dependent malate dehydrogenase (MDH).
- A single functional allele in any of the three mitochondrial MDH loci is sufficient for normal plant development.
- Plants lacking cytosolic MDH activity exhibit normal development, indicating its non-essentiality.
Conclusions:
- Mitochondrial NAD-dependent malate dehydrogenase (MDH) is essential for normal plant embryogenesis.
- Cytosolic MDH is not essential for plant development.
- This study highlights the critical role of a specific dehydrogenase enzyme in plant embryogenesis.