A subclass of cellulose synthase-like M (CslM) proteins that arose through neofunctionalization was recently shown to glycosylate the aglycone core of triterpenoid saponins. In this issue, Hassan et al. demonstrate a simple tool to distinguish between the two major classes of CslM proteins from closely related CslG proteins, and further show that all CslM proteins also likely have a role in cell wall polysaccharide biosynthesis, specifically in type II arabinogalactan formation. These findings provide new insight into how such diverse functions of CslM could be achieved and highlight clear targets for future research.
The cover image illustrates the spatial distribution of pectic polysaccharides within the seed structure. Specifically, it shows an Arabidopsis seed double-labeled with antibodies against un-esterified homogalacturonan (LM19) and rhamnogalacturonan (M22), counterstained with Calcofluor White to highlight cell walls.