Arabinogalactan‐like Glycoproteins from Ulva lactuca (Chlorophyta) Show Unique Features Compared to Land Plants AGPs

Abstract

Arabinogalactan proteins (AGPs) encompass a diverse group of plant cell wall proteoglycans, which play an essential role in plant development, signaling, plant‐microbe interactions, and many others. Although they are widely distributed throughout the plant kingdom and extensively studied, they remain largely unexplored in the lower plants, especially in seaweeds. Ulva species have high economic potential since various applications were previously described including bioremediation, biofuel production, and as a source of bioactive compounds. This article presents the first experimental confirmation of AGP‐like glycoproteins in Ulva species and provides a simple extraction protocol of Ulva lactuca AGP‐like glycoproteins, their partial characterization and unique comparison to scarcely described Solanum lycopersicum AGPs. The reactivity with primary anti‐AGP antibodies as well as Yariv reagent showed a great variety between Ulva lactuca and Solanum lycopersicum AGP‐like glycoproteins. While the amino acid analysis of the AGP‐like glycoproteins purified by the β‐d‐glucosyl Yariv reagent showed a similarity between algal and land plant AGP‐like glycoproteins, neutral saccharide analysis revealed unique glycosylation of the Ulva lactuca AGP‐like glycoproteins. Surprisingly, arabinose and galactose were not the most prevalent monosaccharides and the most outstanding was the presence of 3‐O‐methyl‐hexose, which has never been described in the AGPs. The exceptional structure of the Ulva lactuca AGP‐like glycoproteins implies a specialized adaptation to the marine environment and might bring new insight into the evolution of the plant cell wall.

Arabinogalactan Proteins in Plant Roots – An Update on Possible Functions

“…Structural proteins are a minor but essential component of the primary cell wall (Rui and Dinneny, 2020) and include prolinerich proteins (PRPs), glycine-rich proteins (GRPs), extensins (EXTs), and AGPs. AGPs are present in vascular plants, bryophytes (Bartels et al, 2017;Johnson et al, 2017;Ma et al, 2017;Classen et al, 2019) and green algae (Palacio-Lopez et al, 2019;Přerovská et al, 2021). AGPs or AGP-like proteins have also been detected in brown algae (Herve et al, 2016) and cyanobacteria (Jackson et al, 2012) opening discussion on their evolutionary origin (Knox, 2016).…”

Search for evolutionary roots of land plant arabinogalactan‐proteins in charophytes: presence of a rhamnogalactan‐protein in Spirogyra pratensis (Zygnematophyceae)

“…Nevertheless, when and how the glycan structures of AGPs evolved is still questionable. Using monoclonal antibodies directed against oligosaccharide epitopes, AG-epitopes in different algae have been detected in brown algae ( Hervé et al, 2016 ; Raimundo et al, 2016 ), in chlorophyte green algae ( Estevez et al, 2008 , 2009 ; Přerovská et al, 2021 ) and also in charophyte algae ( Domozych et al, 2009 ; Eder et al, 2008 ; Palacio-López et al, 2019 ; Sørensen et al, 2011 ). It needs to be taken into account that the exact epitopes of these antibodies are often unknown and also show cross-reactivities with other polysaccharides (e.g.…”

Arabinogalactan Protein-Like Proteins From Ulva lactuca Activate Immune Responses and Plant Resistance in an Oilseed Crop

“…To neutralize the samples, 300 mg of BaCO 3 were added and incubated overnight on vortex. Samples were centrifuged at 10,000 g for 15 min, the supernatants were filtrated, and pH was checked ( Přerovská et al, 2021 ). If needed, samples were further diluted to get within the calibration range of the following analysis.…”

“…While the amino acid analysis of the AGP-like glycoproteins purified by the β- d -glucosyl Yariv reagent showed a similarity between Ulva AGP-like glycoproteins and land plant AGPs, saccharide analysis revealed unique glycosylation of the Ulva lactuca AGP-like glycoproteins. Surprisingly, arabinose and galactose were not the most prevalent monosaccharides and the most outstanding was the presence of 3- O -methyl-hexose, which has never been described in the AGPs ( Přerovská et al, 2021 ). Nevertheless, methylation of AGP glycans was previously reported ( Bartels et al, 2017 ; Bartels and Classen, 2017 ; Happ and Classen, 2019 ; Temple et al, 2019 ; Pfeifer et al, 2020 ).…”

“…Within the Chlorophyta division, AGPs were also reported in Oedogoniaceae and Codiaceae families ( Estevez et al, 2008 , 2009 ; Fernández et al, 2010 , 2015 ). Very recently, AGP-like glycoproteins were isolated for the first time from Ulva lactuca ( Přerovská et al, 2021 ). In this study, Ulva AGP-like glycoproteins exhibited a contrasting reactivity with primary anti-AGP antibodies as well as with Yariv reagent when compared to AGP glycoproteins isolated from Solanum lycopersicum .…”