Abstract: The present invention is regarding plants and plant storage organs thereof in which GLP-1 derivatives are accumulated, and methods of producing them. The transgenic plants and plant storage organs thereof accumulate tandem repeated GLP-1 derivatives cleavable with intestinal digestive enzyme to monomeric molecules and are produced by methods comprising: integrating into vectors linked DNAs which comprise tandem repeated DNAs encoding the GLP-1 derivative with trypsin resistance in which the amino acid in the 26th position is Gln, the amino acid in the 34th position is Asn or Asp, and C-terminal consists of Arg or Lys to produce monomeric molecules; introducing the vectors into plant cells; and redifferentiating the obtained transformants. The edible transgenic plants and plant storage organs are useful for treating diabetes and can be ingested by diabetic patients.

Abstract: The present invention provides a method for highly producing a recombinant protein in a plant storage organ and a GLP-1 derivative. The plant storage organ in which the recombinant protein is highly produced is obtained by transformation with the use of a vector which comprises a recombinant protein gene, a cytokinin-related gene, a drug-resistant gene and a removable DNA element, in which the cytokinin-related gene and the drug-resistant gene exist in the positions so that they can behave together with the DNA element, while the recombinant protein to be expressed in the plant storage organ exists in the position so that it would not behave together with the DNA element. The GLP-1 is produced by using the method, and a derivative having been stabilized against enzymatic digestion is further provided.