Production of Quinolizidine Alkaloids by Photomixotrophic Cell Suspension Cultures: Biochemical and Biogenetic Aspects¹

Abstract

The biosynthetic pathway of quinolizidine alkaloids is localized in leaf chloroplasts of Lupit~us polypbyllus. Consequently alkaloid production is up to 4 to 10 times higher in photomixotrophic cell suspension cultures of L. polypbyllus with developed chloroplasts, than in chlorophyll-free heterotrophic culturcs.. . Cell suspension cultures of L , p o l y p l~~l-!US, S. scoparius and B. australis accumulate about 2 to 3 orders less alkaloids as compared with the differentiated plants. In these cultures l~ipanine figures as the only main alkaloid, independent of the alkaloid composition of the respective plants, which is significantly different in -S. scoparius and B. australis. It is concluded that the lupanine pathway is basic for the quinolizidine alkaloids and that the I 1)edicarrd to Proi. Dr. Dr. h .~. mult. KLI<.I. MCYI.H~\ on thc occasion oi his 80th birthday.other alkaloids such as sparteine, 13-hydroxylupanine and the respective ester alkaloids, the tricyclic angustifolines and the a-pyridone alkaloids derive from lupanine. In cell suspension cultures only the basic pathway is expressed whereas the more advanced sequences are missing.

Diurnal Fluctuation of Quinolizidine Alkaloid Accumulation in Legume Plants and Photomixotrophic Cell Suspension Cultures

“…But the alkaloid form ation seems to be positively correlated with greening, i.e. chlorophyll formation of the cultures [7,8]. This is in accordance with the finding that the subcellular site of alkaloid formation is the chloroplast [9,10], Localization of a biosynthesis in the chloroplast raises the question o f light-m ediated control of product formation.…”

“…It should be recalled in this context that alkaloid accumulation in lupin cell cultures is up to 2 orders of magnitude lower than in the differentiated plant [7], although active enzymes of alkaloid biosynthesis are present. Maybe alkaloid formation is active too, but the alkaloids produced are not accum ulated as in the plant but are rapidly degraded.…”

“…We have established photom ixotrophic cell sus pension cultures of L. polyphyllus and S. scoparius which accumulate quinolizidine alkaloids at low levels [7,8]. The alkaloid content of L. polyphyllus cell cultures displays a maximum three days after medium transfer.…”

“…The filtered or centrifuged hom ogenate was alcalinized with 25% ammonium hydroxide and extracted with m ethylene chloride [6,7,13]. Total alkaloid content was deter mined photometrically [6,7] or by capillary gasliquid chromatography (glc), using sparteine (Roth, Karlsruhe) as an external standard.…”

Evidence for a wide‐spread occurrence of the genes of quinolizidine alkaloid biosynthesis

“…3.1. Induction of alkaloid accumulation in ceil suspension cultures of alkaloid-producing species Photoheterotrophic, chloroplast-containing cell suspension cultures to Lupinus polyphylus, Cytisus scoparius and other Fabaceae accumulate quinolizidine alkaloids such as lupanine at a concentration usually l-3 orders of magnitude lower than the alkaloid level of the differentiated plant [4,5], similarly to the situation in many other cell culture systems [l l-131. However, the activity of the enzymes of lupanine biosynthesis, lysine decarboxylase (3,141 and oxosparteine synthase [7,8], which are localized in the chloroplast [9], is similar to, or lower only by one order magnitude than, the respective enzyme activities in the plant [15].…”