The present invention provides methods and compositions for making and using transgenic plants that exhibit increased nitrogen storage capacity compared to wild-type plants. Methods of the invention comprise inducing overexpression of monocot-derived vegetative storage proteins (VSPs) in plants, particularly in monocots. In some embodiments, at least one nucleotide construct comprising a nucleotide sequence encoding the ZmLox6 protein or a biologically active fragment or variant thereof is introduced into a plant. Depending upon the objective, the nucleotide construct may optionally comprise an operably linked coding sequence for a vacuolar sorting signal or plastid transit peptide in order to direct storage of the ZmLox6 protein or biologically active fragment or variant thereof into the vacuolar compartment or plastid compartment, respectively, of the cells in which the VSP is expressed. The invention further provides methods for producing plants with increased nitrogen content and/or increased nutritional value, which is desirable in commercial crops, including those used for forage, silage, and grain production.