Changes in the Growth, Redox Status and Expression of Oxidative Stress Related Genes in Chickpea (Cicer arietinum L.) in Response to Copper Oxide Nanoparticle Exposure

Abstract

Copper oxide nanoparticles (CuONPs) are used in a variety of applications and their release into the environment may lead to the contamination of agricultural fields. However, the toxicity of CuONPs is hard to evaluate due to the lack of knowledge of their toxicity in major food crops. In this study, we investigated the toxic effects of CuONPs in germinating seedlings of chickpea (Cicer arietinum L.). The plants were grown in 1/2 strength Murashige and Skoog medium containing 0, 50, 100, 200, 400, and 500 mg L−1 of CuONPs in a growth chamber at 26 ± 2 °C, 16/8 h light/dark photoperiod for 10 days. The toxic effect of CuONPs was tested on seedling development (shoot, root growth, and fresh weight), reactive oxygen species (ROS) generation, peroxidase (POD) enzyme activity, root lignification, and changes in root anatomy. The expression of the oxidative stress-related genes viz. CuZn-SOD (CuZn-superoxide dismutase), CAT (catalase), and APX (ascorbate peroxidase) were studied using real-time polymerase chain reaction. The CuONPs were toxic to chickpea seedlings and decreased the shoot and root growth. The ROS generation and lipid peroxidation level was high in CuONP-treated seedlings. Significant increases in POD enzyme activity and lignin content were observed with increased CuONPs concentrations. Exposure to different concentrations of CuONPs caused retardation of root growth, excess lignification, and cytotoxicity in root cells. Cross sections of roots exposed to CuONPs showed an increase in the number of xylem vessels and also enhanced lignification of xylem vessels. Expression of the CuZn-SOD and CAT genes did not change in shoots under CuONPs exposure. Significant up-regulation of CuZn-SOD gene was observed in roots upon exposure to different concentrations of CuONPs. The expression of the CAT gene was significantly high under 50, 100, and 200 mg L−1 of CuONPs. However, no significant change in the expression of the CAT gene was observed upon exposure to 400 and 500 mg L−1 of CuONPs. The expression levels of the APX gene did not change in shoots and roots under exposure to different concentrations of CuONPs.