Light regulation of succinate dehydrogenase subunit B gene SDH2-3 expression in maize leaves

Abstract

It has been established that, under light, acute decrease in succinate dehydrogenase (SDH) activity in maize (Zea mays L.) leaves occurs, which is likely due to lowering the role of tricarboxylic acid cycle (TCA) as energy supplier under actively functioning photosynthesis. The mechanism underlying the light regulation of SDH subunit B genes transcription level was clarified. It was shown that, in green maize leaves, mRNA of only gene sdh2-3 encoding large subunit of this enzyme was detected. The apparent absence of transcripts of genes sdh2-1 and sdh2-2 encoding other isoforms of the large subunit of the enzyme is explained by their differential expression on other stages of plant ontogenesis due to metabolism restructuring for triggering photosynthesis operation. It was found that the active form of phytochrome A participates in the regulation of gene sdh2-3 expression, leading to the decrease in the amount of mRNA of the given gene in leaves. Application of specific inhibitor of cell membranes calcium channels (ruthenium red) and EGTA allowed us to reveal that the change in calcium concentration in the nucleus is due to its redistribution between cell compartments, in particular between the nucleus and cytoplasm. In addition, it was found that expression of gene pif3 encoding transcription factor PIF3 is changed in a light-dependent manner, in dependency on the state of the phytochrome system, and this correlates with gene sdh2-3 functioning. These findings may indicate the phytochrome-mediated mechanism of the regulation of this gene with participation in the process of transcription factor PIF3.