A suggested role of galloyl esters in the evolution of dicotyledons

Abstract

Summary Gottlieb, O. R., Kaplan, M. A. C. & Kubitzki, K.: A suggested role of galloyl esters in the evolution of dicotyledons. – Taxon 42: 539–552. 1993. – ISSN 0040‐0262. Galloyl esters (gallo‐ and ellagitannins), which occur throughout the more primitive members of the Hamamelididae, Dilleniidae and Rosidae (the “HDR complex”), are important chemosystematic markers. Their significance is not limited to their strong protein‐binding activity, as was formerly believed, or to their toxic properties, which have more recently been recognized. They also have powerful electron scavenging properties, thus inhibiting oxidation, a reaction that is fundamental in the synthesis of secondary metabolites. The HDR complex indeed is poor in shikimate‐derived compounds; polyketide, mevalonate, and Krebs cycle‐derived substances, which originate primarily by reactions such as condensation, esterification, and reduction, prevail but lack systematic continuity. The absence of coherent chemosystematic markers reflects the systematic isolation of the orders and superorders in the HDR complex, where phylogenetic relationships are less obvious than in the other dicotyledonous subclasses. Phytoalexins are mostly found in members of the HDR complex that are poor in galloyl esters. In view of their molecular properties (small, planar, highly conjugated molecules) it is suggested that they equally act as antioxidants. The superorders belonging to the subclasses Magnoliidae, Caryophyllidae, and Asteridae, which lack galloyl esters, are endowed with antioxidants of weak efficacy (proanthocyanidins and/or caffeic acid esters) and have a rich array of secondary metabolites, which permits the recognition of major evolutionary lines.

Notes on the Evolution of Androecial Organisation in the Magnoliophytina (Angiosperms)

“…1). A pair of characters analogous to the duality oligomery -polyrnery exists in the recognition of major evolutionary lines based on chemical markers (see Gottlieb et al, 1993;Kubitzki and Gottlieb, 1984a, b;Kubitzki, 1993 Floral ontogenetic studies are important as: (1) they present a plausible alternative to overcome preconceived barriers between many and few stamens. as if a condition with "many" stamens is always homologous and conditions with few stamens are always homologous; and (2) the importance of the position of individual stamens in the flower is recognized.…”

Characterization of a UGT84 Family Glycosyltransferase Provides New Insights into Substrate Binding and Reactivity of Galloylglucose Ester-Forming UGTs

“…It was suggested that GA and other highly oxidized (e.g., containing multiple hydroxyl groups) metabolites had evolved during the transition from a general to a more specialized plant defense. , Consequently, the UGTs that modify GA may have evolved from an ancestral UGT that work­(ed) with other metabolites. The structural profile of genistein may resemble that of the sugar acceptor for this ancient UGT enzyme.…”