Abstract text: More than 500 years ago, the first plants colonized the terrestrial environment and enabled life on land. All land plants share a common ancestor with streptophyte algae – the exact evolutionary steps remain still unknown. Successful terrestrialization required major adaptations of the plant cell wall to cope with drought, UV-radiation and mechanical stress. Pectins are the most complex polysaccharides of plant cell walls and play an important role in growth, morphogenesis, development, cell expansion, cell adhesion or interaction with the environment. 
This study investigates the evolution and diversity of the three main pectin classes - homogalacturonan (HG), rhamnogalacturonan-I (RG-I) and rhamnogalacturonan-II (RG-II) -within the streptophyte lineage.
Pectic fractions of 25 species were extracted and analysed regarding their monosaccharide composition and compounds. HG was identified in all land plants through galacturonic acid oligomers, whereas several algae showed no detectable signal. RG-I was detected based on its characteristic monosaccharides; however, microarray signals and sugar profiles suggest that classical RG-I backbones may not have been present in all lineages. In particular, RG-I side chain organization and variability varied strongly among species. In comparison, all investigated tracheophytes possess distinct RG-II structures, including the rare sugars characteristic of RG-II while other streptophytes lack this pectic polysaccharide.