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Partial Wiv-1 cDNA for a cell-wall-bound acid invertase isolated from wounded leaves of tomato (Lycopersicon esculentum) was introduced into tomato plants in an antisense orientation. The enzyme activity was markedly decreased in wounded leaves of 3 of 9 transformants. The soluble sugars and starch contents in the source leaves of these 3 transformants were reduced compared with control plants. These results suggest that the cell-wall-bound acid invertase encoded by Wiv-1 regulates the carbohydrate content in source leaves of tomato. Most of the transformants showed low fertility. It is possible that the enzyme encoded by Wiv-1 participates also in sink metabolism in tomato flowers.

This work was undertaken to investigate the relationship between water status and sucrose metabolism of suspension culture of carrot (Daucus carota L.) cells. Embryogenic callus was induced on carrot hypocotyl in vitro. The cell suspension culture was then produced from this callus.In suspension culture, water potential and pH of the culture solution were decreased immediately after culture initiation to -0.62MPa and 4.5 respectively, but gradually increased from 2 days after culture initiation. Sucrose in suspension culture solution was found to be immediately hydrolyzed into glucose and fructose after the initiation of culture and disappeared within 2 days from culture initiation. The disappearance of sucrose from the culture solution within 2 days of culture initiation corresponds with increases in the activity of cell-wall-bound acid invertase. These results indicate that the decline of water potential of the culture solution at the early stages of carrot suspension culture was associated with sucrose metabolism as a result of an increase in acid invertase activity.

Fragaria×Ananassa Duch. cv. Toyonoka is a main variety of strawberry in Japan, but it is susceptible to a pathogenic fungus, Sphaerotheca humuli. Rice chitinase gene under the control of cauliflower mosaic virus (CaMV) 35S promoter was introduced into the strawberry plants using Agrobacterium tumefaciens. The transgenic plants showed an increased resistance to the powdery mildew, S. humuli.