Crown gall cells of Catharanthus roseus

Metabolism of Castasterone in Crown Gall Cells of Catharanthus roseus. 

The structural relationship between phytosterols and BRs has been proposed from the biosynthetic points of view. All naturally occurring BRs possess carbon skeletons identical to those of common phytosterols (e.g., campesterol, 24-methylene-cholesterol, isofiicosterol, sitosterol, and cholesterol). Thus, BRs may be speculatively regarded as the enzymatic oxidation products of phytosterols with the corresponding carbon skeletons, as is the case of the biosynthesis of other steroid hormones (e.g., ecdysteroids (25) and 1,25-dihydroxyvitamin D3 (26)). Although BL has recently been proved to be biosynthesized from CS in crown gall cells of Catharanthus roseus (27), a major part of the biosynthesis of BRs is remained to be investigated. Experiments using radio-labeled precursors are required to clarify the biosynthesis of BRs in a suitable plant system. 

Castasterone was found to be a biosynthetic precursor of brassinolide using Catharanthus roseus crown gall cells. However, castasterone was not converted to brassinolide in tissues of mung bean and rice, indicating that growth-promoting activity of castasterone observed in these tissues was exerted by castasterone itself. 

Figure 5. Change of Contents of Brassinolide and Castasterone during Growth of Catharanthus roseus Crown Gall Cells...

Figure 6. Reverse Phase (C g Silica) HPLC Analysis of Chloroform-Soluble Fraction Obtained from Catharanthus roseus Crown Gall Cells Fed with Tritiated Castasterone...

An epimeric pair of dehydrodiconiferyl alcohol P-o-gly-cosides (23, 24) from crown gall Agrobacterium tumefa-ciens) tumors in transformed Catharanthus roseus cultures has been shown to promote cell division and replace the cytokinin requirement in tobacco cells (Fig. 8.10) (Binns et al., 1987 Lynn et al., 1987). 

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