Abstract
This study elucidates mechanisms conferring differential tolerance to cadmium (Cd) stress in contrasting pea genotypes. Cd stress caused a significant decline in morphophysiological traits in Hurst Green Shaft but not in Kelvedon Wonder, suggesting that Cd-stress tolerance does exist in Kelvedon Wonder. Results showed a significant increase of Cd in roots of both genotypes but not in leaves of Kelvedon Wonder due to Cd stress. Consistently, RIT1 (Fe transporter) transcript showed downregulation and upregulation in Kelvedon Wonder and Hurst Green Shaft, respectively, in leaves upon Cd exposure. This consistent atomic absorption spectroscopy and expression data suggest that limiting Cd translocation by decreased RIT1 expression is related to the ability of Kelvedon Wonder plants to cope with Cd stress. Furthermore, an enhanced antioxidant activity was only observed in leaves of Kelvedon Wonder under Cd stress. Finally, high-performance liquid chromatography analysis showed elevated cysteine, methionine and glutathione in leaves of Kelvedon Wonder, suggesting better protection of pea plants from Cd-induced oxidative stress. Our findings reveal that differential tolerance to Cd stress is mainly attributed to Cd translocation and antioxidant defense in pea plants, which can be further implemented for Cd-free transgenic peas to limit environmental toxicity and health hazards.