Bioproduction of N⁶-benzyladenine N⁹-b-d-glucopyranoside using suspension cells of bamboo (Phyllostachys nigra)

Abstract

Suspension-cultured cells of a temperate bamboo species (Phyllostachys nigra) accumulate substantial amounts of hydroxycinnamic acid derivatives and lignin under culture conditions that promote xylogenesis. In our previous study, we found a metabolite specifically produced in bamboo cells cultured under lignification-inducing conditions in a medium containing N⁶-benzyladenine (BA), but the chemical structure was not elucidated. In this study, we purified and identified this compound as BA N⁹-b-d-glucopyranoside (BA-9G). Despite the presence of three nitrogen positions (N-3, N-7, and N-9) that may be glucosylated in the adenine moiety of BA, bamboo cells specifically produced BA-9G (i.e., without other glucoside types) when cells were cultured in the presence of BA. This finding suggests that bamboo cells possess a regio-specific N-glucosyltransferase for catalyzing cytokinin glucoside formation. The biological activity of BA-9G as a cytokinin was compared with that of BA on the basis of adventitious shoot formation on internodal segments of ipecac (Carapichea ipecacuanha) plants grown under in vitro conditions. The activity of BA-9G was more moderate than that of BA, but BA-9G was less cytotoxic than BA at a high concentration, suggesting that BA-9G may be useful as a plant growth regulator. The development of a viable system for the regio-specific bioproduction of BA-9G in bamboo cells may increase the availability of this highly expensive and rare cytokinin derivative.