Utilization of Amygdalin during Seedling Development of Prunus serotina

Abstract

Cotyledons of mature black cherry (Prunus serotina Ehrh.) seeds contain the cyanogenic diglucoside @)-amygdalin. The levels of amygdalin, its corresponding monoglucoside (R)-prunasin, and the enzymes that metabolize these cyanoglycosides were measured during the course of seedling development. During the first 3 weeks following imbibition, cotyledonary amygdalin levels declined by more than 80%, but free hydrogen cyanide was not released to the atmosphere. Concomitantly, prunasin, which was not present in mature, ungerminated seeds, accumulated in the seedling epicotyls, hypocotyls, and cotyledons to levels approaching 4 pmol per seedling. Whether this prunasin resulted from amygdalin hydrolysis remains unclear, however, because these organs also possess UDPChandelonitrile glucosyltransferase, which catalyzes de novo prunasin biosynthesis. The reduction in amygdalin levels was paralleled by declines in the levels of amygdalin hydrolase (AH), prunasin hydrolase (PH), mandelonitrile lyase (MDL), and j3-cyanoalanine synthase. At all stages of seedling development, AH and PH were localized by immunocytochemistry within the vascular tissues. In contrast, MDL occurred mostly in the cotyledonary parenchyma cells but was also present in the vascular tissues. Soon after imbibition, AH, PH, and MDL were found within protein bodies but were later detected in vacuoles derived from these organelles.

Protein Storage Vacuoles Are Transformed into Lytic Vacuoles in Root Meristematic Cells of Germinating Seedlings by Multiple, Cell Type-Specific Mechanisms

“…Thus, in aleurone cells, the transformation events also include coalescence of the PSVs, acidification of the vacuole lumen and enzyme activation, and finally mobilization of the stored molecules. Similar sequences of events have been described for the formation of LVs in germinating seeds of Prunus serotina (Swain and Poulton, 1994) and for the generation of large LVs during programmed cell death of endothelial cells in developing Arabidopsis seeds (Ondzighi et al, 2008). In contrast to the simple LV-forming events in the epidermal and outer cortex cells, those that accompany the transformation of PSVs to LVs in the inner cortex (endodermis) and vascular cylinder cells are much more complex in that they involve several additional structural intermediates as well as autophagic vacuoles.…”

Bitterness in Almonds

“…In the bitter genotype that accumulates amygdalin, this opportunity of using the secondary metabolite as a buffer for primary metabolism has been retained. But in contrast to the situation in the sweet variety, this opportunity is exploited when the amygdalin-containing seed is ready to germinate and the amygdalin stored in the cotyledons is turned over as happens within a 3-week period for 80% of the amygdalin stored in black cherry seeds (Swain and Poulton, 1994b). Thus cyanogenic glucoside production and accumulation in almonds appears to constitute yet another example where formation of a secondary plant product serves to balance processes in primary metabolism by providing a buffer capacity.…”

“…HCN is an inhibitor of cell respiration and is detoxified by the action of the enzyme b-cyano-Ala synthase, which converts HCN and Cys into b-cyano-Ala (Floss et al, 1965). By the action of nitrilases, b-cyano-Ala is converted into Asn and Asp (Swain and Poulton, 1994b;Piotrowski et al, 2001;Piotrowski and Volmer, 2006;Jenrich et al, 2007;Kriechbaumer et al, 2007).…”

Suppressive Effect of Constituents Isolated from Kernel of Prunus armeniaca on 5 .ALPHA.-Androst-16-en-3-one Generated by Microbial Metabolism

“…However, the quantity of prunasin varied depending on the part of the plant, the species of plant, or seedling stage due to the action of the enzyme group, which was related to the cyanide metabolism (26,27). If we selected the plant species or the part of the plant we could easily prepare a superior extract that outperformed all others.…”