Analysis of Cell-Wall Invertase Function in Leaves of Tomato under Cold Stress

To clarify the function of cell wall invertase in cold stress reaction, antisense-LIN6-transformants of tomato, Micro tom, were treated with low temperature (15°C for 14 h in light of 72 μmol·m^-2·s^-1 and 10°C for 10 h in darkness), taking the wild type as the control. The result showed that the photosynthetic ratio, content of carotenoids and soluble sugar in the transformants´ leaves decreased remarkably. The activity of cell wall invertase in tomato leaves was remarkably correlated with the content of carotenoids and soluble sugar, the activity of cytoplasmic invertase and vacuolar invertase and the photosynthetic rate under low temperature. Therefore, we concluded that cell wall invertase may maintain soluble sugar (especially the nonreductive soluble sugar) and carotenoids at a certain level for keeping high photosynthetic ratio under low temperature stress.