The present invention provides transgenic plants which after harvest degrade the lignin and cellulose therein to fermentable sugars which can further be fermented to ethanol or other products. In particular, the transgenic plants comprise ligninase and cellulase genes from microbes operably linked to a DNA encoding a signal peptide which targets the fusion polypeptide produced therefrom to an organelle of the plant, in particular the chloroplasts. When the transgenic plants are harvested, the plants are ground to release the ligninase and cellulase which then degrade the lignin and cellulose of the transgenic plants to produce the fermentable sugars.