Department of Biotechnology, Institute for Microbial Biotechnology and Metagenomics, University of the Western Cape, Private Bag X17, Bellville, 7535, South Africa.
Planta. 2012 Dec;236(6):1803-15. doi: 10.1007/s00425-012-1731-x. Epub 2012 Aug 19.
The present study reports the effect of high molecular weight bacterial fructan (levan) and glucan (reuteran) on growth and carbohydrate partitioning in transgenic sugarcane plants. These biopolymers are products of bacterial glycosyltransferases, enzymes that catalyze the polymerization of glucose or fructose residues from sucrose. Constructs, targeted to different subcellular compartments (cell wall and cytosol) and driven by the Cauliflower mosaic virus-35S: maize-ubiquitin promoter, were introduced into sugarcane by biolistic transformation. Polysaccharide accumulation severely affected growth of callus suspension cultures. Regeneration of embryonic callus tissue into plants proved problematic for cell wall-targeted lines. When targeted to the cytosol, only plants with relative low levels of biopolymer accumulation survived. In internodal stalk tissue that accumulate reuteran (max 0.03 mg/g FW), sucrose content (ca 60 mg/g FW) was not affected, while starch content (<0.4 mg/g FW) was increased up to four times. Total carbohydrate content was not significantly altered. On the other hand, starch and sucrose levels were significantly reduced in plants accumulating levan (max 0.01 mg/g FW). Heterologous expression resulted in a reduction in total carbohydrate assimilation rather than a simple diversion by competition for substrate.
本研究报告了高分子量细菌果聚糖（西聚糖）和葡聚糖（莱菔坦）对转基因甘蔗植物生长和碳水化合物分配的影响。这些生物聚合物是细菌糖基转移酶的产物，这些酶能催化从蔗糖中聚合葡萄糖或果糖残基。通过弹道转化法，将针对不同亚细胞区室（细胞壁和细胞质）的构建体，由花椰菜花叶病毒 35S:玉米泛素启动子驱动，导入甘蔗中。多糖的积累严重影响了愈伤组织悬浮培养物的生长。胚胎愈伤组织向植物的再生对于细胞壁靶向的系来说是有问题的。当靶向细胞质时，只有相对低水平生物聚合物积累的植物才能存活。在积累莱菔坦（最高 0.03 mg/gFW）的节间茎组织中，蔗糖含量（约 60 mg/gFW）不受影响，而淀粉含量（<0.4 mg/gFW）增加了四倍。总碳水化合物含量没有明显改变。另一方面，积累西聚糖（最高 0.01 mg/gFW）的植物中淀粉和蔗糖水平显著降低。异源表达导致总碳水化合物同化减少，而不是通过竞争底物简单转移。
