It is intended to construct a system for arbitrarily expressing a desired gene at a desired site in a plant. This object can be solved by providing a plant containing at least one promoter allowing a specific level of expression and a gene ligated to this promoter in an operable manner wherein the specificity of the promoter is determined based on the expression frequency of a gene containing the promoter in a cDNA database involving the promoter-containing gene. As a cDNA database, use may be made of those published in the genome project.