Actively growing Trichosanthes kirilowii var. Japonicum root culture grown under light produces two proteins that are similar to the S1 and S2 proteins (expansin) extracted from Cucumis sativus cv Burpee Pickler stems. These proteins play a role in the expansion (swelling) of cell walls. Since the root cultures can be easily handled and scaled up, root cultures may be an alternative source for the production of expansin.