Involvement of auxin and nitric oxide in plant Cd-stress responses

Cadmium (Cd) toxicity inhibited the seedling growth while inducing the occurrences of lateral roots (LR) and adventitious roots (AR). Further study indicated that auxin and nitric oxide (NO) are involved in the processes. In this study, we chose model plant Arabidopsis thaliana and Cd-hyperaccumulator Solanum nigrum as material to examine the involvement of Cd-induced auxin redistribution in NO accumulation in plants and the effect of NO on Cd accumulation. For this aim, the histochemical staining, NO fluorescence probe (DAF-2DA) detections combined with the pharmacological study were used in this study. By using DR5:GUS staining analysis combined with NO fluorescence probe (DAF-2DA) detection, we found that Cd-induced NO accumulation is at least partly due to auxin redistribution in plants exposure to Cd. Supplementation with SNP donor S-nitrosoglutathione (GSNO) increased the number of LR and AR. In contrast, NO-scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl imidazoline-1-oxyl-3-oxide (cPTIO) reversed the effects of NO on modulating root system architecture and Cd accumulation. These results suggest that manipulation of the NO level is an effective approach to improve Cd tolerance in plants by modulating the development of LR and AR, and provide insights into novel strategies for phytoremediation.