Free and conjugated polyamines in wild and transgenic types of Nicotiana tabacum calli

Mohamed I. Abdelhady¹, Amira Abdel Motaal², Rehab Kamel³ and Omar A. Rashwan²

¹Pharmacognosy Department, Faculty of Pharmacy, Helwan University, (Egypt) ²Pharmacognosy Department, Faculty of Pharmacy, Cairo University, Cairo (Egypt) ³Pharmacology Department, Faculty of Pharmacy, Helwan University, (Egypt)

ABSTRACT: Homospermidine synthase (HSS) is a branch-point enzyme that links the secondary pathway (pyrrolizidine alkaloids) to the primary metabolism (polyamines). Since the diamine putrescine is a precursor of homospermidine and nicotine in tobacco, we performed expression of a Senecio vernalis homospermidine synthase gene (hss) in Nicotiana tabacum and determined the effect on free and conjugated polyamine levels in the callus. The hss gene from Senecio vernalis was placed under the control of the cauliflower mosaic virus (CaMV) 35S promoter in Agrobacterium tumefaciens Ti-plasmid and both constructs were transformed into tobacco plants (transformation was previously done, under publication). Seeds of the first generation were used in this study. Expression of the hss gene in callus was verified by western blot. The transgenic sense line was generated showing strong expression of HSS. These transgenic sense calli showed a significantly decreased level of free spermidine while the pool of total spermidine was not affected. Homospermidine was not detected in wild type tobacco under our conditions, while its level was highly increased in the transgenic line.

KEYWORDS: Nicotiana tabacum; homospermidine synthase; callus; polyamines; alkaloids

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