Presence of Dihydrofolate Reductase in Seedlings and Callus of Nigella Sativa L. Plant.

The study aimed to investigate the biosynthesis of thymidine nucleotide by salvage and de novo pathways in the black seed (Nigella sativa L.) plant. The results indicated the absence of thymidine phosphorylase activity in the cell extract of black seed plant while dihydrofolate reductase was present. This may indicate that black seed cells depend on de novo pathway for dTMP synthesis.
Callus induction occurred on stem segments of Nigella sativa L. seedlings grown on Murashige and Skoog medium, containing 10-6M of 2,4-D .
Specific activity of dihydrofolate reductase and total folate content of black seed callus reached 24,13,8,4 and 3 folds than that found in seeds, roots, flowers, stems and leaves respectively.
Moreover, the results indicated an increase in the fresh weight with an increase in the cellular contents of proteins, nucleic acids (DNA and RNA) and folate extracted from callus of deferent ages. The specific activity of dihydrofolate reductase followed the same pattern of the cell components.