Progress towards the genetic engineering of tomato fruit softening

Previous studies have correlated the softening of tomato fruit to changes in cell wall structure and the activities of cell wall degrading enzymes. In particular, the pectin-degrading enzyme polygalacturonase (PG) has been associated with softening. Studies of ripening-mutants deficient in PG activity have furthered this association. Recent advances in plant genetic engineering have enabled researchers to control PG gene expression, and to investigate further the role of this enzyme in fruit softening. The status and future directions of these experiments are discussed.