Functional overlap of two major facilitator superfamily transporter, ZIF1, and ZIFL1 in zinc and iron homeostasis

Zinc and iron are essential micronutrients for plant growth, and their homeostasis must be tightly regulated. Previously, it has been shown that Zinc-Induced Facilitator 1 (ZIF1) is involved in basal Zn tolerance by controlling the vacuolar storage of nicotianamine (NA). However, knowledge of the functional roles of two ZIF1 paralogs, ZIF-LIKE1 (ZIFL1) and ZIFL2, in metal homeostasis remains limited. Here, we functionally characterized the roles of ZIF1, ZIFL1, and ZIFL2 in Zn and Fe homeostasis. Expression of ZIF1 and ZIFL1 was induced by both excess Zn and Fe-deficiency, and their loss-of-function led to hypersensitivity under excess Zn and Fe-deficiency, suggesting functional overlap between ZIF1 and ZIFL1. By contrast, the disruption of ZIFL2 resulted in no obvious phenotypic alteration under both conditions. Additionally, the expression of ZIFL1, but not that of ZIFL2, in the zif1 mutant partially restored the phenotype under excess Zn, suggesting that ZIF1 and ZIFL1 perform functionally redundant roles in Zn homeostasis.