assessment of homospermidine synthase (hss) differential expression in different tissues of common groundsel (senecio vulgaris l.) using real-time pcr

the first pathway-specific enzyme for pyrrolizidine alkaloid (pa) biosynthesis is homospermidine synthase. hss catalyzes the nad1-dependent transfer of an aminobutyl group of spermidine to putrescine. putrescine, spermidine and spermine are three polyamines which are naturally positively charged compounds found in virtually all living cells. these compounds bind to dna and have been implicated in a number of crucial processes such as cell division, differentiation and membrane function. very few studies on expression of homospermidine synthase gene in senecio vulgaris have been reported. the objective of current research was to study homospermidine synthase gene expression in different tissues of s. vulgaris by real-time pcr. the total rna was extracted from roots, shoots (stems and leaves) and flowers, and was converted to cdna. specific primers were designed for hss1 gene and also for the pol ii which was applied as a reference housekeeping gene in the experiment. melting curves of two genes showed the specificity of pcr amplification. evaluation of normalized expression level of hss1 gene showed that the gene was differentially expressed in different organs of s. vulgaris. maximum relative expression (>59-fold change relative to pol ii reference gene) was observed in roots where the homospermidine synthase is activated and homospermidine is produced. interestingly, the gene is also expressed in flowers but with a lower extent (4-fold change relative to housekeeping pol ii gene). as expected the gene shows non-significant relative expression in shoots of the pant where the homospermidine is transported.