Purpose: The effect of gamma rays on metallothionein (MT) expression was studied using the medicinal plant Plantago ovata as the test system. Materials and methods: Western blotting and Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) were used for this purpose. Results: Western blot analysis showed significant induction of metallothionein protein following gamma exposure and that induction was highest at 20 Gy gamma dose. At higher gamma doses (100 Gy) MT expression level declined due to degeneration of cells. MALDI-TOF MS analysis indicated the presence of low molecular weight (7-8 kD) MT molecules following the lower radiation doses. Conclusion: It was concluded from the MALDI-TOF MS result that low gamma exposure leads to expression of MT-like protein. At high doses of gamma ray, MT homologues or MT-like protein were not identified, possibly because they might have precipitated due to uncontrolled cross-linking and non-specific aggregation. © 2013 Informa UK, Ltd.