The Arabidopsis E 1 subunit of the 2-oxoglutarate dehydrogenase complex modulates plant growth and seed production

Isoforms of 2-OGDH E1 subunit are not functionally redundant in plant growth and development of A. thaliana. The tricarboxylic acid cycle enzyme 2-oxoglutarate dehydrogenase (2-OGDH) converts 2-oxoglutarate (2-OG) to succinyl-CoA concomitant with the reduction of NAD . 2-OGDH has an essential role in plant metabolism, being both a limiting step during mitochondrial respiration as well as a key player in carbon-nitrogen interactions. In Arabidopsis thaliana two genes encode for E subunit of 2-OGDH but the physiological roles of each isoform remain unknown. Thus, in the present study we isolated Arabidopsis T-DNA insertion knockout mutant lines for each of the genes encoding the E subunit of 2-OGDH enzyme. All mutant plants exhibited substantial reduction in both respiration and CO assimilation rates. Furthermore, mutant lines exhibited reduced levels of chlorophylls and nitrate, increased levels of sucrose, malate and fumarate and minor changes in total protein and starch levels in leaves. Despite the similar metabolic phenotypes for the two E isoforms the reduction in the expression of each gene culminated in different responses in terms of plant growth and seed production indicating distinct roles for each isoform. Collectively, our results demonstrated the importance of the E subunit of 2-OGDH in both autotrophic and heterotrophic tissues and suggest that the two E isoforms are not functionally redundant in terms of plant growth in A. thaliana.