There is provided an expression method of a target foreign gene in a plant inducedby a chemical substance, which comprises a step of activating with copper ionsa transcription factor encoded by a foreign gene different from the target foreigngene to induce activation of transcription of the target foreign gene by a regionhaving a promoter function contained in the target foreign gene, wherein a nucleotidesequence encoding said transcription factor is contained in a gene constructwhich is constructed so as to comprise a nucleotide sequence of a 5'-untranslatedregion of an arbitrary foreign gene downstream from the region having a promoterfunction contained in the target foreign gene.
