Hemicellulose‐remodelling transglycanase activities from charophytes: towards the evolution of the land‐plant cell wall

作者：Lenka Franková, Stephen C. Fry · 发表于：The Plant Journal · 年份：2021 · DOI：10.1111/tpj.15500 · 被引用次数：24 · 研究领域：Polysaccharides and Plant Cell Walls、Botanical Research and Applications、Microbial Metabolites in Food Biotechnology

SUMMARY Transglycanases remodel cell‐wall polymers, having a critical impact on many physiological processes. Unlike xyloglucan endotransglucosylase (XET) activity, widely studied in land plants, very little is known about charophyte wall‐modifying enzymes – information that would promote our understanding of the ‘primordial’ wall, revealing how the wall matrix is remodelled in the closest living algal relatives of land plants, and what changed during terrestrialisation. We conducted various in‐vitro assays for wall‐remodelling transglycosylases, monitoring either (a) polysaccharide‐to‐[ 3 H]oligosaccharide transglycosylation or (b) non‐radioactive oligosaccharide‐to‐oligosaccharide transglycosylation. We screened a wide collection of enzyme extracts from charophytes (and early‐diverging land plants for comparison) and discovered several homo‐ and hetero‐transglycanase activities. In contrast to most land plants, charophytes possess high trans‐β‐1,4‐mannanase activity, suggesting that land plants’ algal ancestors prioritised mannan remodelling. Trans‐β‐1,4‐xylanase activity was also found, most abundantly in Chara , Nitella and Klebsormidium . Exo‐acting transglycosidase activities (trans‐β‐1,4‐xylosidase and trans‐β‐1,4‐mannosidase) were also detected. In addition, charophytes exhibited homo‐ and hetero‐trans‐β‐glucanase activities (XET, mixed‐linkage glucan [MLG]:xyloglucan endotransglucosylase and cellulose:xyloglucan endotransglucosylase) despite the paucity or lack of la...