The present invention provides a polynucleotide having a function of regulating a content of a plant metabolite, a polypeptide having a function of regulating a content of a plant metabolite, a vector containing the polynucleotide or a part of the polynucleotide, and a transformed plant produced by using the vector. Examples of such polynucleotides or polypeptides include polynucleotides or polypeptides with homology with quinolinate synthase or those which are predicted to be transcription factors. A method for producing the transformed plant is additionally included.
