OsFWL5 limits cadmium accumulation in rice through a proposed vascular-dependent interception and retrieval mechanism

Cadmium (Cd) is a harmful heavy metal that significantly endangers agricultural output and human well-being. This study unveils a novel mechanism by which the rice gene OsFWL5 modulates Cd accumulation and tolerance. We demonstrate that OsFWL5 is transcriptionally induced by Cd and that its encoded protein forms homooligomers. Most importantly, through a detailed histochemical analysis, we show that OsFWL5 exhibits a unique complementary vascular localization: in the root xylem and the shoot phloem. Loss-of-function osfwl5 mutants hyperaccumulated Cd in roots and exhibited heightened sensitivity to Cd stress. Conversely, OsFWL5-overexpressing plants accumulated less Cd and were more tolerant. Based on these findings, we propose a dual 'Interception and Retrieval' model, in which OsFWL5 is posited to intercept Cd loading into the root xylem (limiting its upward transport) and to potentially retrieve Cd from shoots via the phloem, which would promote its redirection to roots. Our results suggest that OsFWL5 is a key regulator of Cd partitioning and a promising candidate for developing low-Cd rice varieties.