A new method for increasing expression of a puroindoline protein in a plant, said puroindoline protein modifying grain hardness, notably breadmaking quality, said method comprising the steps of: (e) preparing a DNA construct which will allow the expression of a puroindoline protein, (f) introducing said DNA construct into plant cell, plant tissue, or plant, (g) selecting the plant cell, or plant tissue, or plant which stably maintain the puroindoline expression, (h) and optionally regenerating fertile stable transformed plant.