Structural investigations on arabinogalactan-proteins from a lycophyte and different monilophytes (ferns) in the evolutionary context

•This contribution provides the first detailed characterization of AGPs from a lycophyte and different monilophytes.•Investigated AGPs share general structural features with AGPs from angiosperms like a protein with Hyp and type II AG moieties.•A special feature of investigated fern AGPs but not Lycopodium AGP is the unusual monosaccharide 3-O-methyl-rhamnose.•A unique attribute of Lycopodium AGP are high amounts of terminal pyranosidic arabinose residues.•The study contributes to better understanding of evolution of AGPs and plant cell wall. Today, understanding of cell wall evolution is incomplete due to limited knowledge of cell wall structure of non-flowering plants. Besides polysaccharides, proteoglycans like arabinogalactan-proteins are important constituents of the cell wall of most if not all seed plants. This article provides the first detailed characterization of AGPs from a lycophyte and different ferns, which are the closest living relatives to seed plants. The amount of protein in fern AGPs (6–12%) was in a range comparable to most seed plant AGPs. However, it was higher for Lycopodium AGP (17%). The carbohydrate moieties of investigated AGPs showed typical features known for type-II arabinogalactans from seed plants and showed cross-reaction with polyclonal antibodies raised against Echinacea AGP. On the other hand, unusual structural components like high quantities of pyranosidic arabinose residues for Lycopodium AGP and 3-O-methyl-rhamnose for fern AGPs have been detected.