Accumulation and Storage

Since the secondary metabolites produced in plant cells have high biological activity, they are potentially toxic to the plant cells themselves. However, metabolite-producing cells can grow without serious disruption of their basic metabolism (Sakai et al., 2002). The regulatory mechanisms of alkaloid accumulation and detoxification in plant cells have been less well studied. Functional analysis of yeast PDR5 (pleiotrophic drug resistance-type ATP-binding cassette transporter) genes in transgenic tobacco (Nicotiana tabacum L.) BY2 cell lines has suggested that these genes can be used to stimulate the secretion of secondary metabolites in plant cell cultures (Goossens et al., 2003a). Recent identification of the function of CjMDR (a multidrug resistance gene) isolated from C. japonica cells for uptake in rhizome may lead to a better understanding of the mechanism of accumulation and detoxification of these biologically active metabolites (Shitan et al., 2003).