Optimization of Biolistic-mediated Gene Transfer Parameters by Transferring Mutansucrase (gtfI) Coding Gene in Sugarcane

Sugarcane (Saccharum officinarum) is the most important industrial sugar producing plant. Both tissue culture practices and transformation are challenging and need to be optimized. A gene encoding a mutansucrase (gtfI) enzyme from Streptococcus downei bacterium was isolated and cloned in a binary expression vector and transferred to sugarcane cultivars, using gene gun and Agrobacterium-mediated transformation. Results of this study showed that Agrobacterium was not able to deliver gtfI gene to sugarcane plants cells, whereas Biolistic gene transfer was successful and resulted in almost 25.7% transformation efficiency. Distance between explant and rupture disc carrying gtfI construct had a significant effect on transformation efficiency with 9cm distance producing the higher number of transformants than 12 cm distance. A combination of sorbitol and mannitol osmoticums showed a profound effect on transformation efficiency. Furthermore, a combination of IBA and NAA auxins had a significant effect on root regeneration. Interestingly, mutansucrase was found active in transgenic sugarcane lines utilizing sucrose by almost 33%. Detailed sugar analysis of a few transgenic sugarcane plants revealed that transgenic plants had a significant lower sucrose (lower pol%) content than untransformed control plants.