ANTISENSE ACID INVERTASE (TIV1) GENE ALTERS SOLUBLE SUGAR COMPOSITIONAND SIZE IN TRANSGENIC TOMATO FRUIT

Invertase (beta-fructosidase, EC 3.2.1.26) hydrolyzes sucrose to hexos e sugars and thus plays a fundamental role in the energy requirements for plant growth and maintenance. Transgenic plants with altered extra cellular acid invertase have highly disturbed growth habits. We invest igated the role of intracellular soluble acid invertase in plant and f ruit development. Transgenic tomato (Lycopersicon esculentum Mill.) pl ants expressing a constitutive anti-sense invertase transgene grew ide ntically to wild-type plants. Several lines of transgenic fruit expres sing a constitutive antisense invertase gene had increased sucrose and decreased hexose sugar concentrations. Each transgenic line with frui t that had increased sucrose concentrations also had greatly reduced l evels of acid invertase in ripe fruit. Sucrose-accumulating fruit were approximately 30% smaller than control fruit, and this differential g rowth correlated with high rates of sugar accumulation during the last stage of development. These data suggest that soluble acid invertase controls sugar composition in tomato fruit and that this change in com position contributes to alterations in fruit size. In addition, sucros e-accumulating fruit have elevated rates of ethylene evolution relativ e to control fruit, perhaps as a result of the smaller fruit size of t he sucrose-accumulating transgenic lines.