Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/1999
Publication Date: N/A
Citation: Interpretive Summary: To the layman, respiration can be thought of as the use of energy by living cells to do work. Important products of this work include growth and reproduction. Respiration must be carefully controlled or energy will be wasted. Wasted energy would decrease crop yields and reduce agricultural productivity. The control of respiration in plant cells is not yet fully understood. The genetic material for an important control step in respiration was isolated from corn and studied. Comparisons were made with similar genetic material from animals and fungi in order to identify which parts might be important in control of respiration. A method was developed to prepare large amounts of the plant products that had full biological activity. Being able to produce large amounts of material will allow detailed analysis of the structures. This information will be important to researchers in their attempts to increase agricultural productivity by altering the control of plant cell respiration and to other plant scientists who will try to design more efficient crop plants through either classical breeding or biotechnology.
Technical Abstract: Four cDNAs, one encoding alpha and three encoding beta subunits, of the mitochondrial pyruvate dehydrogenase were isolated from maize libraries. The deduced amino acid sequences of both alpha and beta subunits are approximately 80% identical with Arabidopsis thaliana and pea homologues. The mature N-terminus was determined for the beta subunit by microsequencing the protein purified from etiolated maize shoot mitochondria and resolved by two-dimensional electrophoresis. The single electrophoretic species was comprised of multiple isoforms. Both alpha and beta subunits are encoded by multigene families in maize as determined by Southern blot analyses. RNA transcripts for both alpha and beta were more abundant in roots than in young leaves or etiolated shoots. Pyruvate dehydrogenase activity was also higher in roots (5-fold) compared to etiolated shoots and leaves. Both subunits were present at similar levels in all tissues examined, indicating coordinated gene regulation. The protein levels were highest in heterotrophic organs and in pollen, which contained about two-fold more than any other organ examined. The relative abundance of these proteins in non-photosynthetic tissues may reflect a high cellular content of mitochondria, a high level of respiration, or both.