Calcium and ethylene glycol tetraacetic acid mitigate toxicity and alteration of gene expression associated with cadmium stress in chickpea (Cicer arietinum L.) shoots

In the aim to estimate the protective role of calcium (Ca) and ethylene glycol tetraacetic acid (EGTA) against cadmium (Cd)–induced damage, chickpea (Cicer arietinum L.) seeds were exposed to 200 μM Cd stress for 6 days or 3 days then subjected to co-treatment of the metal with either 100 mM CaCl2 or 100 μM EGTA for 3 additional days. The addition of Ca and EGTA improved seedling growth. This protecting effect was correlated to the alleviation of the metal-induced oxidative stress, exemplified by the reduction of hydrogen peroxide (H2O2) contents. Besides, Ca and EGTA stimulated thioredoxin (Trx) and thioredoxin reductase (NTR) activities (2.75- and 1.75-fold increase when compared to Cd-stressed, respectively) protecting, thereby, protein –SH groups from the Cd-mediated oxidation, and modulated ferredoxin (Fdx) activity to a control level. Moreover, Ca and EGTA reinstated the glutathione redox steady state, mainly via preserving a high level of glutathione reduced form (GSH). This effect coincided with the maintaining of the Cd-stimulated glutathione reductase (GR) activity and the decline of glutathione peroxidase (GPX, 43% lower than Cd-stressed shoots) activity. Ca and EGTA counteracted the inhibitory effect of Cd on the activity and gene expression of Cu/Zn-superoxide dismutase (Cu/Zn-SOD) isoenzyme and modulated the activities of catalase (CAT) and ascorbate peroxidase (APX). Overall, our results provided evidence that Ca and EGTA supplement could be a promising approach in the remediation of Cd-contaminated environment.