Hetero-trans-β-Glucanase Produces Cellulose-Xyloglucan Covalent Bonds in the Cell Walls of Structural Plant Tissues and Is Stimulated by Expansin  

作　　者：Klaus Herburger Lenka Frankova Martina Picmanova Jia Wooi Loh Marcos Valenzuela-Ortega Frank Meulewaeter Andrew D.Hudson Christopher E.French Stephen C.Fry 

机构地区：[1]The Edinburgh Cell Wall Group,Institute of Molecular Plant Sciences,School of Biological Sciences,The University of Edinburgh,Edinburgh EH93BF,United Kingdom [2]Institute of Quantitative Biology,Biochemistry and Biotechnology,School of Biological Sciences,The University of Edinburgh,Edinburgh EH93BF,United Kingdom [3]BASF,BBCC Innovation Center Gent-Trait Research,9052 Gent(Zwijnaarde),Belgium [4]Zhejiang University-University of Edinburgh Joint Research Centre for Engineering Biology,Zhejiang University,Haining,Zhejiang 314400,China [5]Present address:Section for Plant Glycobiology,Department of Plant and Environmental Sciences,University of Copenhagen,Frederiksberg 1871,Denmark

出　　处：《Molecular Plant》2020年第7期1047-1062,共16页分子植物（英文版）

基　　金：We thank the UK Biotechnology and Biological Sciences Research Council(BBSRC;BB/N002458/1)for funding;K.H.thanks the Villum Foundation(project TIPorNOT 00023089)for financial support during manuscript preparation.

摘　　要：Current cell-wall models assume no covalent bonding between cellulose and hemicelluloses such as xyloglu-can or mixed-linkageβ-D-glucan(MLG).However,Equisetum hetero-trans-β-glucanase(HTG)grafts cellu-lose onto xyloglucan oligosaccharides(XGOs)-and,we now show,xyloglucan polysaccharide-in vitro,thus exhibiting CXE(cellulose:xyloglucan endotransglucosylase)activity.In addition,HTG also catalyzes MLG-to-XGO bonding(MXE activity).In this study,we explored the CXE action of HTG in native plant cell walls and tested whether expansin exposes cellulose to HTG by disrupting hydrogen bonds.To quantify and visu-alize CXE and MXE action,we assayed the sequential release of HTG products from cell walls pre-labeled with substrate mimics.We demonstrated covalent cellulose--xyloglucan bonding in plant cell walls and showed that CXE and MXE action was up to 15%and 60%of total transglucanase action,respectively,and peaked in aging,strengthening tissues:CXE in xylem and cells bordering intercellular canals and MXE in scleren-chyma.Recombinant bacterial expansin(EXLX1)strongly augmented CXE activity in vitro.CXE and MXE ac-tion in living Equisetum structural tissues potentially strengthens stems,while expansin might augment the HTG-catalyzed CXE reaction,thereby allowing efficient CXE action in muro.Our methods will enable surveys for comparable reactions throughout the plant kingdom.Furthermore,engineering similar hetero-polymer formation into angiosperm crop plants may improve certain agronomic traits such as lodging tolerance.

关 键 词：cell wall cellulose hemicelluloses hetero-trans-p-glucanase hetero-transglycosylation xyloglucan 

分 类 号：Q94[生物学—植物学]