Production of recombinant miraculin protein using transgenic citrus cell suspension culture system

Miraculin gene containing the N-terminal signal peptide was introduced into navel orange (Citrus sinensis Osb. var. brasiliensis Tanaka) callus cells by Agrobacterum-mediated transformation. Transgenic somatic embryos were screened on the shoot induction medium containing 25 mg hygromycin L−1. Citrus callus cells were reproduced from the green color somatic embryos on the callus reproduction medium. The obtained transgenic cells were cultured in Murashige and Tucker’s liquid medium containing 50 g sucrose L−1 in a shaking incubator. Similar to the native miraculin, the secreted recombinant miraculin protein formed a disulfide-linked dimer and retained taste-modifying activity. The stability of recombinant protein expression was confirmed over nine generations of callus. This production system can be an excellent alternative for producing various recombinant proteins as well as miraculin.