Abstract
In the current study, we studied the role of signal transduction in aluminum (Al3+)-induced DNA damage and adaptive response in root cells of Allium cepa L. The root cells in planta were treated with Al3+ (800 μM) for 3 h without or with 2 h pre-treatment of inhibitors of mitogen-activated protein kinase (MAPK), and protein phosphatase. Also, root cells in planta were conditioned with Al3+ (10 μM) for 2 h and then subjected to genotoxic challenge of ethyl methane sulfonate (EMS; 5 mM) for 3 h without or with the pre-treatment of the aforementioned inhibitors as well as the inhibitors of translation, transcription, DNA replication and repair. At the end of treatments, roots cells were assayed for cell death and/or DNA damage. The results revealed that Al3+ (800 μM)-induced significant DNA damage and cell death. On the other hand, conditioning with low dose of Al3+ induced adaptive response conferring protection of root cells from genotoxic stress caused by EMS-challenge. Pre-treatment of roots cells with the chosen inhibitors prior to Al3+-conditioning prevented or reduced the adaptive response to EMS genotoxicity. The results of this study suggested the involvement of MAPK and DNA repair network underlying Al-induced DNA damage and adaptive response to genotoxic stress in root cells of A. cepa.
Highlights
Plant genome is under constant stress from endogenous as well as exogenous factors
MODULATION OF Al3+-INDUCED CELL DEATH AND DNA-DAMAGE Earlier we have reported that Al3+ (≥100 μM) induces DNA damage revealing the involvement of reactive oxygen species (ROS) generated through the Al-triggered oxidative burst (Achary and Panda, 2010; Achary et al, 2012)
mitogen-activated protein kinase (MAPK) cascades relay and amplify signals via three types of reversibly phosphorylated kinases (MAPKKK, MAPKK, and MAPK) leading to the phosphorylation of substrate proteins, whose altered activities mediate a wide array of responses, including changes in gene expression (Mishra et al, 2006; Rodriguez et al, 2010)
Summary
Plant genome is under constant stress from endogenous as well as exogenous factors. Plants being sedentary are uniquely equipped with innate mechanisms that help them to adapt to environmental changes. PARPs and poly(ADP ribose) glycohydrolases (PARGs) are the main enzymes responsible for the posttranslational modification known as poly(ADP-ribosyl)ation implicated in DNA damage response (Briggs and Bent, 2011) These enzymes play important roles in tolerance to genotoxic stress, DNA repair, PCD, transcription, and cell cycle control in plants (Adams-Phillips et al, 2010). In sequel to our earlier studies (Achary and Panda, 2010; Achary et al, 2012, 2013), in the present study we investigated the involvement of MAPK signaling in DNA repair network in the Al3+-induced DNA damage and adaptive response to genotoxic stress in root cells of A. cepa L. subjected to the chosen treatments. Bulbs of A. cepa with growing roots (2–3 cm long) were first conditioned by a 2 h treatment with Al3+ 10 μM (pH 4.5), and after a 2 h inter-treatment interval, were subjected to
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