Effect of Nicotinamide on Gene Expression and Glutathione Levels in Tissue Cultures of Pisum sativum

Abstract

Summary Nicotinamide (NIC; 8.2 mM) caused increased abundance of mRNA for chalcone synthase in shoot and root cultures of Pisum sativum . Increased gene expression was observed from 3.5 h after NIC addition in shoot cultures in light (PS-S) and root cultures in light (PS-R-L) and darkness (PS-R-D). Twelve h after NIC addition to the cultures, the amount of mRNA for chs2 was increased 10-fold in PS-R-L, 6-fold in PS-R-D and 2-fold in PS-S. The expression of the glutathione reductase (GR) gene and the photosynthetic cab gene was also studied. Increased GR expression was clearly seen 3.5 h after NIC addition in PSS and PS-R-L and after 12 h in PS-R-D cultures, while the amount of mRNA for cab initially (2–3.5 h) increased and later ( 6–12 h) decreased in PS-S. Glutathione content was determined in the cultures. After a decrease in glutathione content during the first 2–3.5 h following NIC addition, the level of glutathione increased. In light-grown cultures, an increase in the content of the oxidised (disulfide) form of glutathione (GSSG) was an earlier event than the rise in reduced glutathione (GSH) levels, after 12h for PSR- L and after 3.5-6h for PS-S. Five days after NIC addition, the GSSG contents in the root and shoot cultures in light were increased by up to 150 and 500%, respectively, whereas the amounts of GSH doubled in both cultures. In dark grown cultures, an early increase in the content of GSH, but not GSSG, was observed.