Alterations in transcriptome and proteome on metallothioneins following oxidative stress induced by sublethal doses of cadmium and gamma rays in Plantago ovata

Abstract

Purpose: To study the oxidative stress-induced changes by sublethal doses of cadmium chloride (CdCl₂) and gamma irradiation, two redox-inducing agents, on metallothionein (MT) gene and protein expression in Plantago ovata Forsk (P. ovata).

Materials and methods: Chlorophyll content was estimated to study the stress response in P. ovata seedlings following exposure to gamma irradiation and CdCl₂. Lipid peroxidation and proline content, two oxidative stress markers, were also studied. The level of metallothionein gene and protein expression was further investigated using polymerase chain reaction (PCR), reverse transcription-PCR (RT-PCR), immunocytochemistry and flow cytometry.

Results: Three MT genes of P. ovata namely PoMT 1, PoMT 2 and PoMT 3 were isolated, sequenced and characterized and their expressions were found to be altered in the case of both oxidative stresses in a dose-dependent and tissue-specific manner. The results were in agreement with the observations from immunocytochemistry and FACS analysis.

Conclusions: The results suggest that both gamma irradiation and CdCl₂ alter redox balance in P. ovata. The metallothionein gene may play an important role in metal tolerance and stress balance. It is conjectured that the stress-mediated imbalance is maintained by altered MT gene and protein expression.

Keywords::

• Plantago ovata
• metallothionein
• oxidative stress
• reverse transcription PCR
• flow cytometry
• immunocytochemistry

Acknowledgements

Authors would like to thank Dr Avijit Saha, UGC-DAE Consortium for Scientific Research, Kolkata Centre, Radiation Biology Division, India, for providing the cobalt-60 (⁶⁰Co) gamma irradiation facility and Dr Sanjaya Mallick (Application Scientist, BD Bioscience, CRNN) for his invaluable assistance in confocal microscopy imaging and FACS analysis.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

The first author is grateful to UGC-DAE-CSR for financial assistance. Grant no: UGC-DAE-CSR/KC/CRS/09/RB-04/1337 dt 31/07/2009.