Briefly described, embodiments of this disclosure include polynucleotides that encode mutant Cnidarian luciferases that exhibit modulated properties as compared to the corresponding wild-type luciferases, and the modulated properties include at least one of: modulated stability; enhanced light output; and modulated emission maximum. Embodiments of the present disclosure also include polypeptides or fragments thereof encoded by the polynucleotides, constructs including the polynucleotide, expression cassettes, cells, methods of producing the polynucleotides and polypeptides, antibodies, transgenic cells and/or animals, kits, and the like.