Phaseolus vulgaris and Pisum sativum, representing ureide and amide legumes respectively, exploit ureides differentially to mitigate the deleterious effects of cadmium toxicity

Abstract

Abstract Purpose Ureides, allantoin and allantoate, are N-rich compounds used for N transport in nodulated ureide legumes. Here, we investigated their role in response of Phaseolus vulgaris and Pisum sativum, representing ureide and amide legumes, respectively, to Cd toxicity. Methods First, ureide content and ureide metabolism in P. vulgaris and P. sativum grown under control conditions and treated with 50 μM CdCl2 for 48 hours was investigated. Then, the effect of exogenous allantoin and its precursor, uric acid, on Cd-related oxidative lesion was examined in both legumes. Results Cd increased the content of both ureides only in the leaves of P. vulgaris, which was consistent with transcript levels and activity of ureide metabolic enzymes, and was accompanied by an increase in uric acid content. In P. sativum leaves, Cd increased the activity of ureide biosynthesis enzymes and decreased the activity of ureide degradation enzymes, although the uric acid content did not change, while the allantoin and allantoate contents were significantly reduced. Exogenous uric acid and allantoin suppressed Cd-induced H2O2 and O2 accumulation and alleviated the effects of oxidative damage measured by RNA degradation, chlorophyll and malondialdehyde content in both legumes. Conclusions P. sativum use allantoin and uric acid as antioxidant agents to mitigate Cd-related oxidative tissue damage. In P. vulgaris, the involvement of the ureide pathway in Cd-induced N salvage and recycling is rather a priority.