Molecular and Biochemical Aspects of Light Regulation of 2-Oxoglutarate Dehydrogenase in Plants

Molecular and epigenetic mechanisms for regulation of a key TCA enzyme 2-oxoglutarate dehydrogenase (2-OGDH) were investigated in connection with plant metabolism response to alteration of light conditions. It was shown that the activity of 2-OGDH in the leaves of maize (Zea mays L.) depends on illumination. In the dark, the operation of the examined enzyme accelerates what apparently ensures the activation of oxidative processes in mitochondria. In Arabidopsis thaliana (L.) Heynh. plants deficient in the genes of photoreceptors, the mechanism of inhibition of 2-OGDH activity by light (the same as in maize leaves) is mediated via the absorption of red light by phytochrome A and blue light by cryptochrome. The level of transcripts of the genes ogdh-1,ogdh-2, and ogdh-3 encoding peptides of this enzyme complex in maize decreased in the light and upon the exposure to red light; the same reduction was observed for genes ogdh -1 and ogdh-2 in wild-type Arabidopsis. In Arabidopsis plants deficient in the genes of photoreceptors, the regulation of the examined genes was phytochrome- and cryptochrome-dependent. Modification of the extent of methylation of CpG motifs in promoter regions of the genes ogdh-1,ogdh-2, and ogdh-3 under different light conditions suggests that methylation status has a marginal effect on transcription of the examined genes.