Doubled sugar content in sugarcane plants modified to produce a sucrose isomer
Article first published online: 2 NOV 2006
Plant Biotechnology Journal
Volume 5, Issue 1, pages 109–117, January 2007
How to Cite
Wu, L. and Birch, R. G. (2007), Doubled sugar content in sugarcane plants modified to produce a sucrose isomer. Plant Biotechnology Journal, 5: 109–117. doi: 10.1111/j.1467-7652.2006.00224.x
- Issue published online: 17 NOV 2006
- Article first published online: 2 NOV 2006
- Received 1 June 2006; revised 15 September 2006; accepted 17 September 2006.
- Saccharum spp.;
- source–sink relationships;
- sucrose isomerase;
- sugar metabolism
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.