Regulation and Assembly of Pyruvate Dehydrogenase Complexes

University Of Missouri-Columbia, Columbia MO

Investigators

Abstract

Respiration is the use of energy by living cells to do work. Both growth and reproduction are affected by respiration and it must be carefully controlled to avoid decreased growth and, in the case of plants, reduced agricultural productivity. Despite considerable research, details of how respiration is controlled in plant cells remain a puzzle. Pyruvate dehydrogenase is a multi-component enzyme complex located within a specific sub-cellular compartment of plant cells. It occupies a cross-roads position where there is interaction among multiple components of respiration. This complex is ideally situated to play a major role in the overall control of respiration. Furthermore, the multi-component architecture of the complex allows input from several different mechanisms. One element of the regulatory scheme may be an intrinsic component of the pyruvate dehydrogenase complex. Detailed biochemical and molecular analyses of this component will provide critical insight into the putative mechanism of control. In addition, a genetic strategy that uses whole plants will be employed. A small model plant, mouse-eared cress, will be used. Molecular genetic experiments will allow the complete elimination of the proposed control component of the pyruvate dehydrogenase complex. If the control hypothesis is correct, uncontrolled respiration will result in small, less-productive plants. These plants will be rescued by replacing the control component. Both the native control component and versions that have been modified in the laboratory will be used. This will allow specific understanding of the mechanism of control. In contrast to microbes or animals, plant cells contain several different versions of another component of the pyruvate dehydrogenase complex. Preliminary studies have shown that the situation is not so simple as having different versions functioning at different times or in different places. Again, the mouse-eared cress plant will be manipulated so as to eliminate two of the three versions of this component. These experiments will be iterative and combinatorial. This means that plants will be generated that contain only component 1, only 2, only 3, 1 and 2, 1 and 3, and 2 and 3. These manipulations will allow a better understanding of the contribution that each component makes to the whole complex. A third component of the pyruvate dehydrogenase complex has been an enigma. There is considerable evidence for its existence, but it has thus far not been isolated. Attempts to isolate this component by molecular genetics have not been successful. The return to a more classical biochemical isolation strategy will be undertaken. However it will be a more specific strategy based upon results from other plant and animal experimental systems. Isolation of this third component will allow subsequent isolation of the gene. Once this is accomplished, then the biochemical and molecular strategies described above will be applied. The information gained from these experiments will improve basic understanding of plant growth and development. Furthermore, there is the potential that the results will allow researchers to increase agricultural productivity by altering the control of plant cell respiration. Finally, the results will inform the design of more efficient crop plants through classical breeding or biotechnology.