June 9, 2005 | David F. Coppedge

Roses Are Red, Darwinists Are Blue

Roses have a special pigment molecule, a particular form of anthocyanin, responsible for all the rich red-to-blue shades in the petals that delight gardeners and attract pollinating insects.  This molecule is different from the pigments in every other flowering plant; it is glycosylated at two positions instead of one.2  A single enzyme does the job at both points.  Without the glycosylation reaction at both ends, the molecule is unstable and cannot be soluble in water in the vacuoles of the cells in which it operates.
    A team of Japanese scientists investigated how this double-glycosylation reaction system might have evolved.  They could find no intermediate.  Reporting in Nature,1 they said that while other flowers use derivatives from a singly-glycosylated form, “this is evolutionarily precluded in roses by their different glycosylation pattern, which may be unique to members of the Rosaceae” (emphasis added in all quotes).  They also stated with puzzlement,

It is a mystery why this particular glycosyltransferase evolved independently in roses.  The novelty of the RhGT1 enzyme therefore lies not only in its ability to catalyse glycosylation at two different sites on the anthocyanidin molecule but also in its apparent absence from other species.

They prepared a phylogenetic tree based on this type of pigment-preparing enzyme family, but it ended up with the rose family on a branch all by itself.

1Ogata et al., “Plant biochemistry: Anthocyanin biosynthesis in roses,” Nature, 435, 757-758 (9 June 2005) | doi: 10.1038/nature435757a.
2Glycosylation replaces an OH (hydroxyl) group with a glucoside.  This is performed by an enzyme called a glycosyltransferase, in the case of roses, RhGT1.

Here is a small gap, but a gap nonetheless; no evidence for the evolution of this complex molecule and the enzyme that knows how to operate it – just an unconfirmed prediction from evolutionary theory.  Surprised?  Question: was evolutionary theory of any value in this investigation?

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Categories: Botany

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