SEC14-GOLD protein PATELLIN2 binds IRON-REGULATED TRANSPORTER1 linking root iron uptake to vitamin E

Abstract

Organisms require micronutrients, and Arabidopsis (Arabidopsis thaliana) IRON-REGULATED TRANSPORTER1 (IRT1) is essential for iron (Fe2+) acquisition into root cells. Uptake of reactive Fe2+ exposes cells to the risk of membrane lipid peroxidation. Surprisingly little is known about how this is avoided. IRT1 activity is controlled by an intracellular variable region (IRT1vr) that acts as a regulatory protein interaction platform. We found that IRT1vr interacted with peripheral plasma membrane SEC14-Golgi dynamics (SEC14-GOLD) protein PATELLIN2 (PATL2). SEC14 proteins bind lipophilic substrates and transport or present them at the membrane. To date, no direct roles have been attributed to SEC14 proteins in Fe import. Here, PATL2 affected root Fe acquisition responses, interacted with ROS response proteins in roots, and alleviated root lipid peroxidation. PATL2 had high affinity in vitro for the major lipophilic antioxidant vitamin E compound α-tocopherol. Molecular dynamics simulations provided insight into energetic constraints and the orientation and stability of the PATL2-ligand interaction in atomic detail. Hence, this work highlights a compelling mechanism connecting vitamin E with root metal ion transport at the plasma membrane with the participation of an IRT1-interacting and α-tocopherol-binding SEC14 protein.

Role of SEC14-like phosphatidylinositol transfer proteins in membrane identity and dynamics

“…The CTN-SEC14 module of PATL2 was found to govern membrane association of the protein, and the GOLD domain to specify plasma membrane localization, presumably by recognizing PI(4,5)P2 maybe through its lysine motif (Montag et al, 2020). A hint linking PATLs to plasma membrane protein regulation and membrane trafficking is the observation that PATL1 and PATL2 were able to interact with plasma membrane proteins (Chu et al, 2018;Zhou et al, 2018;Hornbergs et al, 2022) (Fig. 4).…”

“…Subsequently, endomembrane trafficking may affect the regulation of IRT1 (Hornbergs et al, 2022). In this context, it is interesting to note that phosphorylation of the N region was identified under Fe deficiency (Lan et al, 2011) and during salt stress, in response to oligogalacturonides, and brassinosteroid signaling (Tang et al, 2008;Hsu et al, 2009;Chang et al, 2012;Mattei et al, 2016), indicating that protein interaction of PATL2 with IRT1 may be under control of protein phosphorylation of the interacting N region.…”

“…Through its GOLD domain PATL1 interacted with CALMODULIN-4 (CaM4), a multifunctional sensor for Ca 2+ , and via its N region it interacted with SALT OVERLY-SENSITIVE 1 (SOS1), a Na+/H+ antiporter localized at the plasma membrane (Chu et al, 2018;Zhou et al, 2018). Its closest homologue PATL2 interacted through its N region with IRON-REGULATED TRANSPORTER 1 (IRT1), an essential protein for iron acquisition by roots in soil (Hornbergs et al, 2022) (Fig. 4B).…”

Review: Role of the plant-specific calcium-binding C2-DOMAIN ABSCISIC ACID-RELATED (CAR) protein family in environmental signaling

“…IRT1 was found to be essential for iron utilization in Arabidopsis (Henriques et al, 2002;Varotto et al, 2002;Vert et al, 2002). IRT1vr is a protein interaction platform to regulate cellular metal ion uptake and IRT1 protein abundance in root cells (Cointry and Vert, 2019;Hornbergs et al, 2022). The EHB1/CAR6 protein interaction with IRT1vr has been validated in yeast two hybrid experiments (IRT1vr as bait, EHB1 as prey) and by bimolecular fluorescence complementation (BiFC) in transiently transformed plant cells of the tobacco leaf epidermis.…”

Metal health: PATELLIN2 reduces iron-induced toxicity in Arabidopsis

“…The current model hypothesizes that PATL2 might make the antioxidant α-tocopherol available where lipid peroxidation is occurring, alleviating oxidative damage. Further work will be required to confirm if α-tocopherol or another component is binding to PATL2 in vivo (Modified figure from Hornbergs et al (2023) made by J.M.U. using Affinity Designer 2 Version 2.0.3).…”