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

Abstract

Lupinus, Baptisia, Sarothamnus, Diumal Rhythm, Photomixotrophic Cell Suspension Cultures, Quinolizidine AlkaloidsFluctuations of quinolizidine alkaloid content in leaflets of Lupinus polyphyllus, L. hartwegii, Baptisia australis, and Sarothamnus scoparius were studied over a 36 h period. The alkaloid contents reached their maximum at noon or early afternoon, and their minimum during the night. The amplitudes of diumal variations in alkaloid levels lay within a range of 60 to 470% of the early morning contents of alkaloids (= 100%) in leaves. In photomixotrophic cell suspension cul tures of L. polyphyllus and S. scoparius cultured under day-night regime, a similar increase of the alkaloid levels was observed within 5 to 8 h after onset of illumination. A subsequent excretion of the alkaloids produced, which also followed a diumal rhythm, was found. S. scoparius cells ex creted lupanine, L. polyphyllus cells 13-cinnamoyloxylupanine. From the cell culture and plant ex periments it can be assumed that the alkaloids which are formed during illumination are trans located to some degree afterwards. In cell suspension cultures the alkaloids are subjected to rapid and rhythmic turnover. Exogenous alkaloids, fed to the cultures, are taken up by the cells and dis appear usually within the first 72 h. A possible mechanism for a light-mediated regulation of quinolizidine alkaloid biosynthesis which was found to be localized in leaf chloroplast, is dis cussed.

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

“…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]. We concluded that lupin alkaloids are actually formed by the cells, but are not accumulated to a marked degree, since they are rapidly degraded which is also an important feature of lupin plants and of other plant species [16,17]. Thus, the alkaloid turnover seemed to us an interesting possibility for the manipulation of alkaloid metabolism.…”

Plant Cell Biotechnology

“…In addition to the biosynthesis of aromatic amino acids, the synthesis of terpenoids from mevalonic acid and part of the synthesis of conine have been shown to take place here. The role of chloroplasts is confirmed by the localization of enzymes involved in the synthesis oflupanine and sparteine in chloroplasts from Lupinus polyphyllus cell suspension cultures (Wink and Hartmann 1982). In Capsicum chromoplasts the stroma is the site of synthesis for the carotenoid phytoene.…”

Chemical Defense of Lupins. Mollusc-Repellent Properties of Quinolizidine Alkaloids

“…QA were extracted and determ ined according to standard methods as outlined in previous papers [2,4,6,7],…”

“…Decaying lupins, however, were readily consumed. All these experiments with intact plants had the dis advantage that the alkaloid content of lupins is variable within plants and within tim e [4] and that other mollusc repellent compounds m ight also be present which could obscure the influence of alkaloids. Therefore we have devised experim ents em ploy ing "artificial" diets, to which specified am ounts of QA were added, so QA content was the only variable of the system.…”

“…The biochemistry and physiology of QA biosynthesis in plants and cell suspension cultures of Lupinus polyphyllus has been studied in detail in our laboratory: The biosynthesis using lysine as the only precursor [1], takes place in the aerial green parts of the lupin and could be local ized in the leaf chloroplast [2,3]. QA are formed only in the light following a diurnal rhythm [4,5]. The QA are then translocated from the leaf via the phloem [6] to all the other plant organs [2], in case of Cytisus (Sarothamnus) scoparius even to its root parasite Orobanche rapum-genistae [7].…”