SORTING NEXIN1 Is Required for Modulating the Trafficking and Stability of the Arabidopsis IRON-REGULATED TRANSPORTER1

Abstract

Dicotyledonous plants growing under limited iron availability initiate a response resulting in the solubilization, reduction, and uptake of soil iron. The protein factors responsible for these steps are transmembrane proteins, suggesting that the intracellular trafficking machinery may be involved in iron acquisition. In search for components involved in the regulation of Arabidopsis thaliana iron deficiency responses, we identified the members of the SORTING NEXIN (SNX) protein family. SNX loss-of-function plants display enhanced susceptibility to iron deficiency in comparison to the wild type. The absence of SNX led to reduced iron import efficiency into the root. SNX1 showed partial colocalization with the principal root iron importer IRON-REGULATED TRANSPORTER1 (IRT1). In SNX loss-of-function plants, IRT1 protein levels were decreased compared with the wild type due to enhanced IRT1 degradation. This resulted in diminished amounts of the IRT1 protein at the plasma membrane. snx mutants exhibited enhanced iron deficiency responses compared with the wild type, presumably due to the lower iron uptake through IRT1. Our results reveal a role of SNX1 for the correct trafficking of IRT1 and, thus, for modulating the activity of the iron uptake machinery.

The dynamics of plant plasma membrane proteins: PINs and beyond

“…SNX1, in particular, appears to control variations in PIN2 degradation in gravistimulated roots and mediates PIN2 retrieval from late endosomes in response to increased temperature, thus linking retromer activity to adaptive growth responses (Jaillais et al, 2006;Kleine-Vehn et al, 2008a;Hanzawa et al, 2013). SNX1 has also been implicated in the recycling of internalized IRT1 from late endosomes to prevent its premature degradation (Ivanov et al, 2014). The VPS35A retromer subunit, by contrast, appears to be required for the functionality of late endosomal compartments, reflecting the differing functions of distinct elements of the plant retromer machinery (Nodzynski et al, 2013).…”

The Vacuolar Manganese Transporter MTP8 Determines Tolerance to Iron Deficiency-Induced Chlorosis in Arabidopsis

“…This may serve to limit the influx of those metals (Barberon et al, 2014). Correct trafficking of IRT1 to the plasma membrane requires the endosomal regulatory protein SNX1 (Ivanov et al, 2014). In addition, IRT1 has been shown to be ubiquitinated for degradation by a RING E3 ubiquitin ligase, IDF1 (Shin et al, 2013).…”

ZINC FINGER OF ARABIDOPSIS THALIANA12 (ZAT12) Interacts with FER-LIKE IRON DEFICIENCY-INDUCED TRANSCRIPTION FACTOR (FIT) Linking Iron Deficiency and Oxidative Stress Responses

“…Fe acquisition is down-regulated under conditions of sufficient and excessive Fe supply in order to prevent the detrimental effects of excess free Fe in the cell (Vert et al, 2003;Ivanov et al, 2014). Through its participation in the Fenton chemistry (Fenton, 1894;Winterbourn, 1995), this free excess Fe leads to the generation of reactive oxygen species (ROS), which in turn cause cellular damage.…”