The present invention provides nucleic acid molecules derived from Nicotiana alata, which encode defensin-like molecules. The present invention contemplates the use of such nucleic acid molecules in the generation of transgenic plants having resistance or at least reduced sensitivity to plant pests including insects, microorganisms, fungi and/or viruses and the of the encoded defensin-like molecules in compositions for topical application to a plant or a plant part so as to reduce prevent or reduce infestation of the plant or plant part by plant pests. The transgenic plants provided by the present invention include monocotyledonous and dicotyledonous plants, and particularly include crop plants and ornamental flowering plants.