Evaluation of Cd(2+) stress tolerance in transgenic rice overexpressing PgGPx gene that maintains cellular ion and reactive oxygen species homeostasis

Non-essential toxic heavy metal like cadmium (Cd(2+)) interferes with the plant growth and development in many ways. Cd(2+) travels via plant transportation system, specifically through xylem and may integrate into the food chain causing unfavorable condition in human health. Therefore, strategies to develop Cd(2+) tolerance and less accumulation in the plant system require urgent attention. Peroxidase gene family is known for metal ions transportation including Cd(2+) and thus plays an important role in ion homeostasis. Previously, we have reported the presence of a Cd(2+) dependent functional peroxiredoxin from Pennisetum glaucum (PgGPx). The present study elucidates the role of this PgGPx against Cd(2+) stress in rice. The transcript levels of PgGPx were found to be highly upregulated in response to exogenous Cd(2+). Moreover, recombinant PgGPx protein showed significant glutathione S-transferase activity in vitro. Ectopically expressed PgGPx in transgenic rice plants showed tolerance towards Cd(2+) stress as demonstrated by several physiological indices including shoot and root length, biomass, chlorophyll, and hydrogen peroxide content. Moreover, these transgenic plants also showed enhanced capability to cope up with oxidative stress by enhancing the activity of different antioxidant enzymes including Superoxide dismutase, Catalase, Ascorbate peroxidase, Glutathione peroxidase, Glutathione reductase) in response to Cd(2+). Hence, maintenance of cellular ion homeostasis and modulation of reactive oxygen species-scavenging pathway are found to be improved by overexpression of PgGPx under Cd(2+) stress. These results will pave the way to develop strategies for engineering Cd(2+) stress tolerance in economically important crop plants.