Sulfur is limiting the glucosinolate accumulation in nasturtium in vitro plants (Tropaeolum majus L.)

It is well established that sulfate fertilisation significantly enhances the content of mustard oil glucosides in glucosinolate containing plants. However, with respect to tissue cultures and in vitro-plants, corresponding data are missing. In this study the influence of sulfur on the accumulation of glucosinolates was analyzed in nasturtium in vitro-plants (Tropaeolum majus). The glucotropaeolin content in plants grown on standard media (MS) varied between 10 and 50 μmol/g DW, corresponding to only about 20 % to 70 % of the glucotropaeolin content in earth grown plants. A fivefold enhancement of the sulfate concentration resulted in a massive increase in the glucotropaeolin content of the in vitro-plants. A decline of sulfate in the medium leads to corresponding diminutions of the glucosinolates accumulated. These data clearly demonstrate the high impact of sulfur availability on glucosinolate biosynthesis and accumulation

Experimental field cultivation of in vitro propagated high-yield varieties of Tropaeolum majus L.

About 10,000 mass propagated clonal progenies of the medicinal plant Tropaeolum majus L. had been cultivated in an experimental field trial to analyze the large scale cultivation of nasturtium-plants for pharmaceutical utilization. The glucotropaeolin contents of the eight Tropaeolum-clones, which had been established and propagated by in vitro-culture techniques, had been monitored and compared with unselected plants from commercial seed mixtures (sm-plants). Whereas the intra-clonal variation of the glucosinolate levels was significantly lower than the variability of the sm-plants, the glucotropaeolin content in the clonal progenies was markedly lower than in both, in the clonal mother plants as well as in the sm-plants. The proposed explanation for this phenomenon is based on the fact that the genetically identical cloned plants reveal only a very narrow phenotypical amplitude, which accordingly resulted in designated glucosinolate levels due to the certain environmental situations. However, under changing conditions, the corresponding glucotropaeolin content might be much lower. In contrast, the sm-plants reveal – due to the strong genetic heterogeneity – a much broader phenotypical amplitude of their physiological characteristics. Consequently, under changing growth conditions various individual plants may accumulate high amounts of glucotropaeolin. These coherences explain both, firstly, the finding that the clonal mother plants revealed very high glucotropaeolin levels under the certain – maybe spatial limited cultivation conditions – whereas their progenies accumulate far less glucosinolates; and secondly, that the average content in the sm-plants is higher than the mean content of the clonal progenies.These data suggest that the much cheaper growing of nasturtium plants from seeds should be favoured over the more sophisticated in vitro-propagation techniques. Anyhow, for industrial farming there is one great advantage for the usage of in vitro generated Tropaeolum plants: the selected, high glucosinolate-nasturtium clones all reveal a compact growth with short tendrils. Therefore, the mechanical harvest of the corresponding clonal progenies, is quite unproblematic in comparison to the difficile harvest of sm-plants, most exhibiting tendrils of several meters

In vitro regeneration of parsley and coriander plants: uptake, translocation and accumulation of nicotine

It is well known that, nicotine is a type of alkaloids found in some plants of family Solanaceae but some other plants can produce it under different stresses. Medicinal and spice plants cannot synthesize nicotine under normal growth conditions as well as the fate and behavior of nicotine in plant tissues are not understood totally. Many medicinal plants and plant derived products as spices may be contaminated by nicotine from different sources. This contamination could be considered the main problem facing the exportation of these plant products. On the other hand, determining of nicotine putative sources and detecting its uptake from nicotine contaminated soils and tobacco smoke using peppermint plants have been already studied under greenhouse conditions in Germany. These results from pot experiments demonstrated that, peppermint had the ability to uptake and metabolize nicotine endogenously. So, some plants including parsley and coriander were selected to investigate the nicotine uptake mechanism from culture media supplemented with different nicotine concentrations, which extracted from cigarette tobacco (Matosian Egyptian Spirit) comparing with nicotinic acid (as a pure chemical of nicotine) in Egypt. Moreover, this in vitro study aimed to focus on the translocation and accumulation of nicotine in plant tissues. Hence, in virto research has been already begun using parsley and coriander plants. The preliminary results indicated that, regenerated plants of parsley and coriander were successfully obtained on MS medium supplemented with 1 mg L-1 benzyl adenine + 0.01 mg L-1 naphthalene acetic acid. Furthermore, callus cultures have been initiated on MS medium fortified with 1 mg L-1 benzyl adenine + 1 mg L-1 naphthalene acetic acid. Regenerated plants and obtained callus of these plants will be transferred onto MS media supplemented with different concentrations of nicotine and nicotinic acid as mentioned above. In parallel, some field experiments in Egypt have been conducted to get a holistic overview for the object under investigation. Therefore, different experiments including field, pots and in vitro experiments have been conducted in order to reduce the contamination of plants with nicotine

Overexpression of Hydroxynitrile Lyase in Cassava Roots Elevates Protein and Free Amino Acids while Reducing Residual Cyanogen Levels

Cassava is the major source of calories for more than 250 million Sub-Saharan Africans, however, it has the lowest protein-to-energy ratio of any major staple food crop in the world. A cassava-based diet provides less than 30% of the minimum daily requirement for protein. Moreover, both leaves and roots contain potentially toxic levels of cyanogenic glucosides. The major cyanogen in cassava is linamarin which is stored in the vacuole. Upon tissue disruption linamarin is deglycosylated by the apolplastic enzyme, linamarase, producing acetone cyanohydrin. Acetone cyanohydrin can spontaneously decompose at pHs >5.0 or temperatures >35°C, or is enzymatically broken down by hydroxynitrile lyase (HNL) to produce acetone and free cyanide which is then volatilized. Unlike leaves, cassava roots have little HNL activity. The lack of HNL activity in roots is associated with the accumulation of potentially toxic levels of acetone cyanohydrin in poorly processed roots. We hypothesized that the over-expression of HNL in cassava roots under the control of a root-specific, patatin promoter would not only accelerate cyanogenesis during food processing, resulting in a safer food product, but lead to increased root protein levels since HNL is sequestered in the cell wall. Transgenic lines expressing a patatin-driven HNL gene construct exhibited a 2–20 fold increase in relative HNL mRNA levels in roots when compared with wild type resulting in a threefold increase in total root protein in 7 month old plants. After food processing, HNL overexpressing lines had substantially reduced acetone cyanohydrin and cyanide levels in roots relative to wild-type roots. Furthermore, steady state linamarin levels in intact tissues were reduced by 80% in transgenic cassava roots. These results suggest that enhanced linamarin metabolism contributed to the elevated root protein levels