A mode of a polypeptide according to the present invention exhibits a fluorescence property, and has (1) an amino acid sequence represented by SEQ ID NO. 1 or NO. 2, (2) an amino acid sequence represented by SEQ ID NO. 1 or NO. 2 in which amino acid sequence 1 to 34 amino acids have been replaced or otherwise modified, (3) a sequence identity of 85% or more with respect to the amino acid sequence represented by SEQ ID NO. 1 or NO. 2, or (4) an amino acid sequence encoded by a polynucleotide that hybridizes under a stringent condition with a polynucleotide having a sequence complementary to a polynucleotide that encodes the polypeptide defined in (1).
