Transformed root organ cultures

Compartment devices have also been used with root-organ cultures to study the contribution of AM hyphae to Cs and U uptake. In one instance, AM fungi and Agrobacterium rhizogenes (Ri-T-DNA)-transformed carrot roots (Declerck et al, 1998) were cultivated in compartmentalized Petri plates, in liquid or gelified media, where hyphal and root uptake were compared. Such devices are very useful to study the potential uptake of elements by AM hyphae in the absence of any other microorganisms, and are very convenient to use. However, it has not been shown whether transformed roots have comparable absorption capacity when compared to normal roots and to whole plants. 

Storage capacity in a cell culture is available inside the cells (e.g., vacuoles) or in the extracellular compartment. The storage facilities of the latter can be remarkedly improved by the addition of liquid organic phases, resins, or other sorbents to the medium. Addition of XAD-7 to Catharanthus roseus cultures resulted in increased yields of indole alkaloids (SS). Addition of a dimethylsiloxane polymer to Eschscholtzia californica cultures improved yields of benzophenanthridine alkaloids ( 9), and increased yields of nicotine and anabasine were obtained by adding of XAD-2 and XAD-4 resins to Nicotiana transformed roots (90,91). 

These findings are in agreement with previous reports that have determined the presence of the h6hgem in anthers and roots of related plant species [12, 53, 109]. Suzuki et al. [53] analyzed the h6h gene expression in several organs of belladona by RT-PCR and in situ hybridization. In this sense, they foimd that the / (5ARNA was present in cultures of transformed roots, normal roots and anthers [53]. However, in stem, leaves, pistils and petals were not possible to detect the hShPAAK as well as in 5. Candida stems and leaves [29, 86]. The role of the H6H enzyme localized in anthers is a subject of debate [53]. It is well known that the enzyme requires hyoscyamine and other co-factors for the proper catalytic activity [12, 24, 29, 110]. 

Pitta-Alvarez, S. 1. and Giulietti, A. M. (1999) Influence of chitosan, acetic acid and citric acid on growth and tropane alkaloid production in transformed roots of Brugmansia Candida. Effect of medium pH and growth phase. Plant Cell Tissue and Organ Culture. 59, 31-38. 

Hilton, M. G. and Rhodes, M. J. C. (1994) The effeet of varying levels of Gamborg s B5 salts and temperature on the accumulation of starch and hyoscyamine in batch cultures of transformed roots of Datura stramorrium. Plant Cell, Tissue and Organ Culture. 38,45-51. 

Rhodes, J. C., Parr, A., Giulietti, A. M., and Aird, E. H. (1994) Influence of exogenous hormones on the growth and secondary metabolite formation in transformed root cultures. Plant Cell Tissue and Organ Culture. 38, 143-151. 

Senecionine N-oxides can be regarded as the backbone structure of many, if not most, macrocyclic PAs of the senecionine type [3]. Tracer studies with root cultures of Senecio species having different PA patterns, synthesize senecionine AT-oxide as the first common alkaloid [21,58]. To a limited extent roots are able to transform senecionine N-oxide into species-specific derivatives. These transformations proceed slowly and are separated in time and space from senecionine N-oxide synthesis [21, 24, 58]. In studies with five Senecio species shoots were found to be the major sites of species-specific alkaloid transformation [59]. In all species tested, leaves, stems, and inflorescences catalyze the transformation of senecionine N-oxide yielding the species-specific alkaloid patterns. The transformations proceed slowly and may vary between shoot organs in their efficiency and even specificity. All transformations established by tracer techniques represent specific reactions that proceed in a position-specific and stereoselective manner (Fig. 6). The stereospecificity and the fact that different Senecio species... 

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