2:"P. pastoris" has two alcohol oxidase genes, "Aox1" and "Aox2", which include strongly inducible promoters. These two genes allow "Pichia" to use methanol as a carbon and energy source. The AOX promoters are induced by methanol, and repressed by glucose. Usually, the gene for the desired protein is introduced under the control of the "Aox1" promoter, which means that protein production can be induced by the addition of methanol on medium. After several researches, scientists found that the promotor derived from "AOX1" gene in "P. pastoris" is extremely suitable to control the expression of foreign genes, which had been transformed into the "P. pastoris" genome, producing heterologous proteins.