Tolerance to cadmium toxicity and phytoremediation potential of three Brassica rapa CAX1a TILLING mutants

Abstract

Cadmium (Cd) is one of the most toxic heavy metals that reduces crop productivity and is a threat to all the food chain including human health. Phytoremediation is an environmentally friendly strategy to clean up soil contaminated with heavy metals. Researchers are selecting new varieties with an enhanced capacity for phytoremediation purposes. Three Brassica rapa mutants for CAX1 transporter were obtained through TILLING. The objective of this work is to evaluate the tolerance of these mutants to Cd toxicity and its potential for Cd phytoremediation. For this, the mutants and the parental R-o-18 were grown under control and Cd toxicity conditions (100 µM CdCl2) and growth, Cd accumulation and physiological parameters were analyzed. The results show that BraA.cax1a mutation provides greater Cd uptake capacity although only BraA.cax1a-12 would be useful for phytoremediation because it registered more than three-fold the Cd content of R-o-18 and presented greater Cd tolerance. This tolerance could be due to the higher Ca and Mg accumulations, the maintaining of photosynthesis performance, the enhanced ROS detoxification and AsA/GSH and TCA cycles, the higher malate, and GA4 concentrations and the lower ethylene levels. Briefly, this study identifies BraA.cax1a-12 as a potential mutant for phytoremediation of Cd contaminated soil and identifies possible physiological elements that contribute to this capacity.