Sequence, Evolution and Expression of Mitochondrial Genomes in the Genus Zea

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Mitochondria help to turn food into chemical energy in cells of plants and animals. Although the nucleus contains the vast majority of the cell's genes, mitochondria have their own DNA, coding for proteins vital for the survival of cells. In animals and most plants, mitochondrial genes are inherited only through the female (egg) parent. Plant mitochondrial genomes are generally much larger and more variable than those of animals. Plant mitochondria code for more proteins, including ones that can interfere with the development of pollen. This type of infertility (which does not affect female parts of flowers) is called cytoplasmic male sterility (CMS). The CMS trait can be exploited in the production of stronger and higher-yielding hybrid plants. Despite their relatively small sizes and importance, very few plant mitochondrial genomes have been sequenced. Mitochondrial protein-coding genes appear to be very similar in different types of plants; however, most of the mitochondrial DNA lies between genes and its function and origin is unknown. Furthermore, it appears that these "intergenic" DNA sequences have little in common in different plants. Therefore, in order to understand how rapid changes occur in plant mitochondrial DNA, we need to analyze mitochondrial genomes from very closely related species. We will sequence the mitochondrial genomes from four types of cultivated maize and one of its close wild relatives, as well as from two other more distantly related monocot crop species, Tripsacum dactyloides (eastern gamma grass) and sorghum. We will identify all the potential genes and look at how they are expressed in different tissues and stages of development. The project will contribute to an understanding of the content, organization, expression and evolution of mitochondrial genomes i