title: Cytosolic invertase contributes to the supply of substrate for cellulose biosynthesis in developing wood.
abstract: Carbon for cellulose biosynthesis is derived from sucrose. Cellulose is synthesized from uridine 5'-diphosphoglucose (UDP-glucose), but the enzyme(s) responsible for the initial sucrose cleavage and the source of UDP-glucose for cellulose biosynthesis in developing wood have not been defined. We investigated the role of CYTOSOLIC INVERTASEs (CINs) during wood formation in hybrid aspen (Populus tremula × tremuloides) and characterized transgenic lines with reduced CIN activity during secondary cell wall biosynthesis. Suppression of CIN activity by 38-55% led to a 9-13% reduction in crystalline cellulose. The changes in cellulose were reflected in reduced diameter of acid-insoluble cellulose microfibrils and increased glucose release from wood upon enzymatic digestion of cellulose. Reduced CIN activity decreased the amount of the cellulose biosynthesis precursor UDP-glucose in developing wood, pointing to the likely cause of the cellulose phenotype. The findings suggest that CIN activity has an important role in the cellulose biosynthesis of trees, and indicate that cellulose biosynthesis in wood relies on a quantifiable UDP-glucose pool. The results also introduce a concept of altering cellulose microfibril properties by modifying substrate supply to cellulose biosynthesis.
authors.affiliation: Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE 901 83, Umeå, Sweden.
authors.forename: Umut
authors.initials: U
authors.lastname: Rende
authors.affiliation: Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE 901 83, Umeå, Sweden.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Chemistry, Umeå University, SE 901 87, Umeå, Sweden.
authors.forename: Madhavi Latha
authors.initials: ML
authors.lastname: Gandla
authors.affiliation: Department of Chemistry, Umeå University, SE 901 87, Umeå, Sweden.
authors.forename: Leif J
authors.initials: LJ
authors.lastname: Jönsson
authors.affiliation: Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE 901 83, Umeå, Sweden.
authors.forename: Totte
authors.initials: T
authors.lastname: Niittylä
mesh_terms: D002482:Cellulose / Q000096:biosynthesis*; D003460:Crystallization; D003600:Cytosol / Q000201:enzymology*; D018506:Gene Expression Regulation, Plant; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D055442:Metabolome; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D032107:Populus / Q000201:enzymology*; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012995:Solubility; D013379:Substrate Specificity; D059467:Transcriptome / Q000235:genetics; D014197:Trees / Q000235:genetics; D014934:Wood / Q000201:enzymology*; D043324:beta-Fructofuranosidase / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger; D002482:Cellulose; D043324:beta-Fructofuranosidase; D005947:Glucose
keywords: 
  Populus
  ; aspen; cell wall; cellulose; invertase; wood