Discovery of Sucrose Metabolizing and Related Genes to Enhance Sugarcane Productivity

Abstract

Phosynthetic carbon asimilation is a major determinant that limits growth and productivity in plants. Study on the activities of the carbon assimilating enzymes revealed that among the enzymes activity of sucrose-phosphate synthase (SPS, EC. 22.4.1.14) is fluctuated in parallel with sucrose content and growth of sugarcane. Cloning of the genes encoding for SPS found the presence of two cDNA clones, SoSPS1 and SoSPS2, in sugarcane and the transcript of SoSPS1 to be predominant in leaves, but that of SoSPS2 to be distributed conservatively in all tissues. To increase sucrose accumulation, the SoSPS1 gene was overexpressed in transgenic tomato and sugarcane. As the consequences, the activity of SPS and sucrose content was significantly increased in leaves of the transgenic plants, but not concomitant followed by significant increase of sucrose contents in the sink tissues of both transgenic plants. This discrepancy of sucrose accumulation might because have not accompanied by sucrose loading mechanism between leave as a source and sink tissue. Thus, the SoSUT1-cDNA encoding for sucrose transporter protein was cloned from sugarcane and double overexpression of SoSPS1 and SoSUT1 increased sharply sucrose content in sugarcane stem and fruit production in tomato. With regard to sucrose content, it is well reported that sucrose acts as a potent osmoprotectant that might induce drought stress tolerant. Whether the increased of sucrose content in transgenic sugarcane induce the drought tolerant is still remain to be elucidated. In addition, identification of a gene responsible for drought tolerance found a SoDip22-cDNA encoding for a hydrophilic protein with molecular mass of 15.9 kDa and the function might to adapt to drought stress. However, the drought stress tolerant sugarcane recently was achieved by genetic engineering of glycine betaine content.