Expansins are proteins that induce extension in isolated plant cell walls in vitro and have been proposed to disrupt non-covalent interactions between hemicellulose and cellulose microfibrils. Because the plant primary cell wall acts as a constraint to cell enlargement, this process may be integral to plant cell expansion and studies of expansins have focused on their role in growth. We have discovered an expansin (Ex1) from tomato, melon and strawberry that is highly abundant and specifically expressed in ripening fruit, a developmental period when growth has ceased but when selective disassembly of cell wall components is pronounced. Also disclosed are expression vectors containing the (Ex1 coding sequence, expression vectors containing an Ex1 sequence in the antisense orientation, Ex1 proteins, and transgenic plants which express both sense and antisense exogenous Ex1.
