Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/21/2005
Publication Date: N/A
Citation: N/A Interpretive Summary:
Technical Abstract: In eukaryotes, the dihydrolipoamide acetyltransferase (E2) subunit of the mitochondrial pyruvate dehydrogenase complex (mtPDC) forms the multi-meric core of the complex to which the other components bind. Analyses of plant mitochondria suggest that a mono-lipoyl form of E2 exists in all species. In addition, some dicot plants contain two distinct forms of E2, a characteristic that appears to be unique to plants. Three forms of mtPDC E2 were identified in Arabidopsis thaliana. Based on sequence analysis, it is clear that two forms of A. thaliana E2 contain one lipoyl domain (E2IA and E2IB), while one form contains two lipoyl domains (E2II). The E2IA and E2IB protein sequences are over 85% identical to each other, and both are near 50% identical to E2II. Recombinant expression of the A. thaliana proteins demonstrated that all three forms of E2 individually form the icosahedral core of PDC. Activity assays revealed that E2IB has a specific activity over 40 times higher than that of other recombinant E2 proteins, including E2IA and E2II. Analysis of mRNA expression revealed that E2 transcripts varied within and between organs, E2IB being the most prevalent in all samples. Transgenic plants expressing promoter-GUS fusions for E2IB and E2II show that E2 expression can be tissue specific. Although all E2 transcripts are seen in flowers, E2II is predominantly in pollen, whereas E2IB is found in female flower organs. We conclude that all three A. thaliana E2s form functional 60-mer complexes and participate in A. thaliana growth and development.