Wu Luguang, Birch Robert G
Botany Department - SIB, The University of Queensland, Brisbane, Qld 4072, Australia.
Plant Biotechnol J. 2007 Jan;5(1):109-17. doi: 10.1111/j.1467-7652.2006.00224.x.
Sucrose is the feedstock for more than half of the world's fuel ethanol production and a major human food. It is harvested primarily from sugarcane and beet. Despite attempts through conventional and molecular breeding, the stored sugar concentration in elite sugarcane cultivars has not been increased for several decades. Recently, genes have been cloned for bacterial isomerase enzymes that convert sucrose into sugars which are not metabolized by plants, but which are digested by humans, with health benefits over sucrose. We hypothesized that an appropriate sucrose isomerase (SI) expression pattern might simultaneously provide a valuable source of beneficial sugars and overcome the sugar yield ceiling in plants. The introduction of an SI gene tailored for vacuolar compartmentation resulted in sugarcane lines with remarkable increases in total stored sugar levels. The high-value sugar isomaltulose was accumulated in storage tissues without any decrease in stored sucrose concentration, resulting in up to doubled total sugar concentrations in harvested juice. The lines with enhanced sugar accumulation also showed increased photosynthesis, sucrose transport and sink strength. This remarkable step above the former ceiling in stored sugar concentration provides a new perspective into plant source-sink relationships, and has substantial potential for enhanced food and biofuel production.
蔗糖是全球一半以上燃料乙醇生产的原料，也是一种主要的人类食物。它主要从甘蔗和甜菜中收获。尽管通过传统育种和分子育种进行了尝试，但几十年来，优良甘蔗品种中储存的糖分浓度并未提高。最近，已经克隆了细菌异构酶基因，这些酶能将蔗糖转化为植物无法代谢但人类可消化的糖类，且对健康有益。我们推测，合适的蔗糖异构酶（SI）表达模式可能同时提供有益糖类的宝贵来源，并突破植物糖分产量的上限。引入针对液泡区室化定制的SI基因，使甘蔗品系的总储存糖分水平显著提高。高价值的异麦芽酮糖在储存组织中积累，而储存的蔗糖浓度没有任何降低，导致收获汁液中的总糖浓度提高了一倍。糖分积累增强的品系还表现出光合作用、蔗糖运输和库强增加。这一显著超越以往储存糖分浓度上限的进展，为植物源库关系提供了新视角，并在提高食品和生物燃料产量方面具有巨大潜力。
