A receptor-like kinase mutant with absent endodermal diffusion barrier displays selective nutrient homeostasis defects

We thank the Genomic Technologies Facility (GTF) and the Central Imaging Facility (CIF) of the University of Lausanne for expert technical support. We thank Valérie Dénervaud Tendon, Guillaume Germion, Deborah Mühlemann, and Kayo Konishi for technical assistance and John Danku and Véronique Vacchina for ICP-MS analysis. This work was funded by grants from the Swiss National Science Foundation (SNSF), the European Research Council (ERC) to NG and a Human Frontiers Science Program (HFSP) grant to JT and NG. GL and CM were supported by the Agropolis foundation (Rhizopolis) and the Agence Nationale de la Recherche (HydroRoot; ANR-11-BSV6-018). MB was supported by a EMBO long-term postdoctoral fellowship, JEMV by a Marie Curie IEF fellowship and TK by the Japan Society for the Promotion of Sciences (JSPS).Peer reviewedPublisher PD

Impurity Effects on the Energy Gap in Fe-doped Bi2212

We performed scanning tunnelling microscopy/spectroscopy (STM/STS) on Fe-doped Bi2212. The Fe substitution for Cu causes a strong spatial inhomogeneity in STS spectra. The energy gap (Δ1 ∼80mV) has a sub-gap (Δ2 ∼70mV) in some distinct locations on the sample surface. We find that the gap edge peaks are largely depressed and only the sub-gap survives across the region where the spatial modulation of the local density of states is stronger. This indicates, that Δ1 anti-correlates with Δ2.Conference : 20th International Conference on Magnetism, ICM 2015Location : Barcelona, SPAINDate : JUL 05-10, 201

Insights into the Mechanisms Underlying Boron Homeostasis in Plants

Boron is an essential element for plants but is toxic in excess. Therefore, plants must adapt to both limiting and excess boron conditions for normal growth. Boron transport in plants is primarily based on three transport mechanisms across the plasma membrane: passive diffusion of boric acid, facilitated diffusion of boric acid via channels, and export of borate anion via transporters. Under boron -limiting conditions, boric acid channels and borate exporters function in the uptake and translocation of boron to support growth of various plant species. In Arabidopsis thaliana, NIP5;1 and BOR1 are located in the plasma membrane and polarized toward soil and stele, respectively, in various root cells, for efficient transport of boron from the soil to the stele. Importantly, sufficient levels of boron induce downregulation of NIP5;1 and BOR1 through mRNA degradation and proteolysis through endocytosis, respectively. In addition, borate exporters, such as Arabidopsis BOR4 and barley Bot1, function in boron exclusion from tissues and cells under conditions of excess boron. Thus, plants actively regulate intracellular localization and abundance of transport proteins to maintain boron homeostasis. In this review, the physiological roles and regulatory mechanisms of intracellular localization and abundance of boron transport proteins are discussed

Plant aquaporin trafficking

Plant aquaporin traffickin

Boron Uptake Assay in Xenopus laevis Oocytes

Boron (B) is essential for plant growth and taken up by plant roots as boric acid. Under B limitation, B uptake and translocation in plants are dependent on the boric acid channels located in the plasma membrane. Xenopus leavis oocyte is a reliable heterologous expression system to characterize transport activities of boric acid channels and related major intrinsic proteins (aquaporins). Here, we outline the protocols for expression of boric acid channels and boric acid uptake assay in Xenopus leavis oocytes

Polar localization and endocytic degradation of a boron transporter, BOR1, is dependent on specific tyrosine residues

Boron (B) is essential for plants, but is toxic in excess. Plants have to strictly regulate the uptake and translocation of B. In Arabidopsis thaliana root cells, a boric acid channel, NIP5;1, and a boric acid/borate exporter, BOR1, localize to the outer (facing soil) and inner plasma membrane domains, respectively, under B limitation. The opposite polar localizations of the importer and exporter would enable plant roots to transport B efficiently toward the xylem. In addition, accumulation of the B transporters is controlled by B conditions. When plants are shifted from low to high B conditions, NIP5;1 transcript accumulation is downregulated through mRNA degradation. The BOR1 protein is transported to the trans­Golgi network/early endosome and multivesicular body and finally degraded in the vacuole. We have recently shown that both the polar localization and the endocytic degradation of BOR1 are controlled by at least two tyrosine residues in a large loop located in the cytosol. We also showed that ubiquitination is required for the endocytic degradation of BOR1. Here, we analyzed possible involvement of an additional tyrosine residue (Y414) in the loop region and discuss the pathway of the BOR1 trafficking for polar localization and endocytic degradation of BOR1

TOL proteins mediate vacuolar sorting of the borate transporter BOR1 in <i>Arabidopsis thaliana</i>

<p>Boron (B) is an essential micronutrient for plants; however, it shows cytotoxicity at high concentrations. A borate transporter BOR1 is required for efficient transport of B toward the root stele in <i>Arabidopsis thaliana</i>. BOR1 shows polar localization in the plasma membrane of various root cells toward the stele-side under B limitation. To avoid over-accumulation of B, BOR1 in the plasma membrane is rapidly internalized and transported into the vacuole for proteolysis after high-B supply in an ubiquitination-dependent manner. Although BOR1 has been predicted to be transported into multi-vesicular bodies/late endosomes (MVB/LEs) via the endosomal sorting complex required for transport (ESCRT) machinery, experimental evidence was absent so far. In this study, we investigated the intracellular localization of BOR1 by visualizing endomembrane compartments, and tested the involvement of ESCRT-0-like proteins TOM1-LIKEs (TOLs) in the vacuolar sorting of BOR1. Under low-B conditions, a large portion of cytoplasmic BOR1 was localized in the <i>trans</i>-Golgi networks/early endosomes (TGN/EEs) labeled with VHA-a1 subunit. Pharmacological interference of endosomal recycling using brefeldin A-induced colocalization of BOR1 with RabA5D, which labels recycling vesicles associated with the TGN. On the other hand, under high-B conditions, BOR1 was localized in the inside of TOL5-positive MVB/LEs. To examine the roles of TOL proteins in intracellular trafficking of BOR1, we analyzed BOR1-GFP localization in the TOL quintuple mutant (<i>tolQ; tol2-1tol3-1tol5-1tol6-1tol9-1</i>) after high-B supply. In the <i>tolQ</i> mutant, vacuolar sorting of BOR1 was delayed, while the polar localization of BOR1 was not disturbed. Taken together, BOR1 is constantly transported to the TGN/EE by endocytosis and recycled to the plasma membrane likely via RabA5D-positive endomembrane compartments under low-B conditions. On the other hand, BOR1 is transported to the vacuole via TOL5-positive MVB/LEs under high-B conditions. TOL proteins are required for sorting of ubiquitinated BOR1 into MVB/LE for vacuolar degradation.</p