Rende Umut, Wang Wei, Gandla Madhavi Latha, Jönsson Leif J, Niittylä Totte
Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE 901 83, Umeå, Sweden.
Department of Chemistry, Umeå University, SE 901 87, Umeå, Sweden.
New Phytol. 2017 Apr;214(2):796-807. doi: 10.1111/nph.14392. Epub 2016 Dec 29.
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.
用于纤维素生物合成的碳源自蔗糖。纤维素由尿苷5'-二磷酸葡萄糖（UDP-葡萄糖）合成，但负责初始蔗糖裂解的酶以及发育中木材纤维素生物合成的UDP-葡萄糖来源尚未明确。我们研究了细胞质转化酶（CINs）在杂种山杨（Populus tremula × tremuloides）木材形成过程中的作用，并对次生细胞壁生物合成过程中CIN活性降低的转基因株系进行了表征。CIN活性抑制38 - 55%导致结晶纤维素减少9 - 13%。纤维素的变化表现为酸不溶性纤维素微纤丝直径减小以及纤维素酶消化木材后葡萄糖释放增加。CIN活性降低减少了发育中木材纤维素生物合成前体UDP-葡萄糖的量，这指出了纤维素表型的可能原因。这些发现表明CIN活性在树木纤维素生物合成中具有重要作用，并表明木材中的纤维素生物合成依赖于可量化的UDP-葡萄糖库。研究结果还引入了通过改变纤维素生物合成的底物供应来改变纤维素微纤丝特性的概念。
