Molecular, regulatory. and functional properties of alternative oxidases of non-angiosperm plants

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Biological electron transport chains (ETCs) power life on this planet. All plant cells contain mitochondria which use oxygen while converting carbon molecules, such as sugars, into energy. Plant mitochondria contain two respiratory pathways: the cytochrome c oxidase pathway, which is found in most organisms, including humans, and the alternative oxidase (AOX) pathway, which has a more limited distribution. Despite the fact that AOX transcripts, protein levels, and enzyme activity increase during a wide variety of environmental stresses, the physiological role of AOX is unknown. The long term goal of my research program is to understand the central role that respiratory electron transport plays in metabolic and physiological adaptations to stress. This proposal describes my plans to: (A) identify and examine AOX genes in non-angiosperm (non-flowering) plants and confirm that they are expressed as functional enzymes, (B) test the hypothesis that non-angiosperm plant AOXs are monomeric (composed of one subunit) and are regulated differently than angiosperm AOXs, and (C) test the hypothesis that AOX proteins encoded by different AOX genes are capable of forming heterodimers and that this will influence the catalytic properties of the enzyme.The answers to these questions will help to shed light on the evolutionary history of AOX and, how AOX enzyme activity is regulated, the structure of AOX, and to confirm that AOX is present in all plants. Our results will contribute to an overall understanding of how metabolic flexibility in the mitochondria of plants allows them to cope with environmental stress and can, thereby, contribute to the improvement of crop species. My research program allows for the training of highly qualified personnel in bioinformatics, molecular biology, biochemistry, physiology, and evolution and serves to illustrate how a comparative and integrative approach to biology can contribute to advancing knowledge.