Members of the microalgae family Scenedesmaceae feature individual N-glycan patterns, a shared Man5GlcNAc2 isomer and core alpha1,6-fucosylation

Although protein linked N-glycosylation is well conserved and more or less uniform in all vascular plants, this important posttranslational modification emerged as being species specific within the Chlorella clade, which belongs to the Trebouxiophyceae class. We were interested if this high degree of diversity would also be found in other families, orders and classes of green algae. In this work we have investigated seven species belonging to the Chlorophyceae family Scenedesmaceae. Mass spectrometry of the N-glycans exposed different and hitherto unseen patterns. Thus, this shotgun investigation supports the idea that N-glycans constitute a tool for correct strain or species assignment for many – if not all Chlorophyta or green algae. Chromatography on porous graphitic carbon identified the Man 5 GlcNAc 2 N-glycan in all seven samples as the unusual isomer previously found in Chlamydomonas reinhardtii . This appears to be a hallmark of a large group of green algae. Many glycans were shown to contain deoxyhexose, which for two strains was identified as l -fucose. Once in α1,3-linkage to the innermost N -acetylglucosamine (GlcNAc) as already assumed for other algae strains and once in α1,6-linkage to the innermost N -acetylglucosamine (GlcNAc), a feature hitherto only known from animals. Substantial gene homology indicates that core α1,6-fucosylation emerged before some early eukaryotes engulfed photosynthetic symbionts. • Structural diversity of protein-linked N-glycans is shown to occur not only in the Chlorella clade but also in a different class of green algae indicating it to be a fundamental and wide-spread phenomenon • An isomer of the Man 5 GlcNAc 2 structure that is unusual for protein-linked forms was found in all seven Scenedesmaceae strains investigated, but not in Chlorella clade samples. Having been originally discovered in Chlamydomonas , it appears to be a structural signature of a larger group of algae. • Core α1,6-linked fucose was found in one sample (SAG 211-8c). This is the first description of this structural element in an organism outside the metazoa (animal) branch.