Root-organ culture

Declerck, S., Dupre de Boulois, H., Bivort, C. Delvaux, B. (2003). Extraradical mycelium of the arbuscular mycorrhizal fungus Glomus lamellosum can take up, accumulate and translocate radiocaesium under root-organ culture conditions. Environmental Microbiology, 5, 510-16. 

Rufyikiri, G., Thiry, Y. Declerck, S. (2003). Contribution of hyphae and roots to uranium uptake and translocation by arbuscular mycorrhizal carrot roots under root-organ culture conditions. New Phytologist, 158, 391-9. 

The genus Duboisia consists of three species, D. leichhardtii F. Muell, D. myoporoides R. Br. and D. hopwoodii F. Muell. The leaves of the former two species are a major source of the tropane alkaloids, scopolamine and hyoscyamine [1]. The alkaloid content in Duboisia can be affected by the environment, and a seasonal decline was noted in the scopolamine content between May and September in Australia [18]. Callus and root cultures of Duboisia have been studied with a view to developing a new method to obtain tropane alkaloids more efficiently and the results obtained supported the view that root organ culture is so far the best system for the production of tropane alkaloids [5]. Therefore suitable culture conditions for growth and alkaloid production must be established. 

Rubus ideaus cv. Titan, the shoots were formed on a first passage culture rather than a previously subcultured root organ culture, and feasible micropropagation system using the cultured roots has not been established [47]. 

Production of useful secondary metabolites in callus and root organ cultures... 

In this chapter, production of isoquinoline alkaloids by callus and root organ cultures of ipecac and production of tropane alkaloids by root organ cultures of Duboisia myoporoides-D. leichhardtii hybrid are described. 

Callus and root organ cultures of Duboisia have been studied with a view to develop a new method to obtain tropane alkaloids more efficiently [64-66]. In solanaceous plants, which produce tropane alkaloids, cultured roots produce them but calli do not [65] or only in very small amounts [66]. Root organ culture might be a useful method to produce tropane alkaloids and suitable culture conditions for growth and alkaloid production must be established. In this section, the effects of auxins including lAA chloro-derivatives on the growth and alkaloid yields in root organ cultures of Duboisia myoporoides - D. leichhardtii hybrid are described [67, 68]. 

Heavy metal and radionuclide concentrations in soils increase due to man-made pollution. One of the first entry points of such elements into plant ecosystems is the rhizosphere, defined as the soil under the biological, physical and chemical influence of roots. Arbuscular mycorrhizal (AM) fungi, symbiotic microorganisms associated with the roots of many plant species, provide a direct link between soil and roots and affect metal transfer to plants. The present chapter includes recent laboratory work and some research aspects stiU to be adressed on the contribution of AM fungi to plant metal uptake. The necessity to develop new and adapted approaches, such as compartment devices and root-organ cultures, to separate AM to root contribution to metal uptake is emphasized. Available data may be difficult to compare because they were obtained under different experimental conditions. However, they suggest that the transfer of heavy metals from AM fungi to plants may be metal specific. Further research should focus on the mechanisms involved in reduced or improved uptake of metals by mycorrhizal plants, on AM tolerance to metals and radionuclides and on AM functional diversity in polluted soils. AM contribution to metal uptake should also be quantified to include data in models of plant uptake. 

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. 

Although compartment devices, including root-organ culture, are very useful for studying the relative contribution of AM and roots to element uptake, the results obtained in such conditions caimot be extrapolated to in situ conditions. 

The results of the tracer studies including the elucidation of the stereochemistry involved, provided a firm basis for a biochemical approach to PA biosynthesis, i. e., characterization of the enzymes that catalyze biosynthetic key steps and the specific mechanisms involved in translocation,subcellular accumulation, and metabolism of PAs. Early tracer work was carried out with intact plants to which tracers were applied for days or weeks. Meanwhile, in vitro plant systems, such as cell cultures and root-organ cultures of PA-producing plants are available. Root cultures were found to be excellent systems for biochemical and enzymatic studies of PA biosynthesis [20-22]. Dedifferentiated cell cultures do not synthesize PAs, but retain the ability to accumulate PAs. They are excellent systems to study the membrane transport of PAs and to identify the subcellular storage sites. 

Chabot, S., G. Becard Y. Piche. 1992. Life cycle of Glomus intraradix in root organ culture. Mycologia 84 315-321. 

Mosse, B. C. Hepper. 1975. Vesicular-arbuscular mycorrhizal infections in root organ cultures. Physiol. Plant Pathol. 5 215-223. 

---