β-galactoglucomannan (β-GGM) is a recently discovered primary cell wall polysaccharide, found in Rosid and Asterid eudicots. The enzyme that transfers β-galactose to β-GGM (called MBGT) was already identified in Rosids, but not in Asterids. Ishida, et al have now identified an MBGT from the Asterid tomato. Unexpectedly, it appears that the MBGT activity arose independently in Rosids and Asterids.
The cover art is an illustration of the phylogenetic tree of plant cell wall biosynthetic glycosyltransferases, representing the emergence of MBGT enzyme activities from two different subclades of family GT47 subgroup A.