1 Dept. of Plant Molecular Physiology, Univ. of Hawaii 2 USDA/ARS at Hawaii Agriculture Research Center
Earlier studies reported that the sucrose content of mature sugarcane stem internodes was negatively correlated to soluble acid invertase (SAI, EC 3.2.1.26) activity, which was considered to be confined primarily in the vacuole. However, in those previous studies, the sugarcane plants used for comparison were either different genotypes, or grown under different environments, or sampled at different developmental stage, all of which are known to affect the level of SAI activity. Therefore, conclusions drawn from those studies were not certain. Previously, we have reported that increased invertase activities in cell wall and in the cytosol cause a decrease in the sucrose content in the sugarcane callus cells. In present study, we are trying to suppress the SAI activity by introducing an anti-SAI construct into sugarcane cells and then determine the resulting sucrose level. A sugarcane soluble acid invertase cDNA, scinvm, was isolated from Molokai 5829 (Saccharum robustum), a low sucrose accumulating variety. A portion of the cDNA was placed under control of the maize Ubi-1 promoter in the antisense orientation. This construct was transformed into sugarcane embryogenic calli derived from H62-4671, a high sucrose accumulating cultivar. The antisense gene suppressed acid invertase activity up to 50% in the soluble fraction, and 25%-30% in the cell wall fraction in the cultured cells. The resulting sucrose level in the transgenic cells was increased about 2 fold. These results indicate that SAI activity is indeed a limiting factor in the sucrose accumulation process of sugarcane .
Plant & Animal Genome VII Conference Plant & Animal Genome VII Conference