Expression of the mammalian Xenotropic Polytropic Virus Receptor 1 (XPR1) in tobacco leaves leads to phosphate export

Abstract

Edited by Ulf-Ingo FlüggeKeywords: PHO1 Phosphate export Tobacco Transporter XPR1 a b s t r a c t Phosphate homeostasis in multicellular eukaryotes depends on both phosphate influx and efflux. The mammalian Xenotropic Polytropic Virus Receptor 1 (XPR1) shares homology to the Arabidopsis PHO1, a phosphate exporter expressed in roots. However, phosphate export activity of XPR1 has not yet been demonstrated in a heterologous system. Here, we demonstrate that transient expression in tobacco leaves of XPR1-GFP leads to specific phosphate export. Like PHO1-GFP, XPR1-GFP is localized predominantly to the endomembrane system in tobacco cells. These results show that tobacco leaves are a good heterologous system to study the transport activity of members of the PHO1/ XPR1 family.

The EXS Domain of PHO1 Participates in the Response of Shoots to Phosphate Deficiency via a Root-to-Shoot Signal

“…This is in accordance with the recent finding that the SPX domain of the mammalian PHO1 homolog XPR1 is also not required for Pi export (Giovannini et al, 2013;Wege and Poirier, 2014). However, expression of the SPXtruncated 4TMEXS protein was unable to complement the pho1 mutant and even strongly exacerbated the reduction in shoot growth.…”

“…Transient expression of fusion proteins in N. benthamiana leaves was used as the preferred experimental system, since colocalization of PHO1-GFP with subcellular markers in Arabidopsis roots has proven to be inadequate due to the combination of poor resolution and weak expression of fluorescent marker proteins in root xylem parenchyma cells . Furthermore, expression of either the Arabidopsis PHO1 or its human homolog XPR1 in N. benthamiana has previously been shown to mediate specific Pi export, revealing that N. benthamiana leaf is an appropriate tissue in which to assess PHO1 Pi export activity Wege and Poirier, 2014).…”

“…1B) were first cloned into the Gateway entry vectors pDONR207 or pENTR2B (Invitrogen) and then transferred into the binary plant expression vectors pMDC43, pMDC83, pMDC7, pMDC132, modified p*7WG2, pYFN43, pYFC43, and pSS01 (Karimi et al, 2002;Curtis and Grossniklaus, 2003;Brach et al, 2009;Zimmerli et al, 2012;Wege and Poirier, 2014).…”

“…The mammalian PHO1 homolog, named XPR1, was initially identified as a protein acting as a cell surface receptor for retroviruses (Battini et al, 1999;Yang et al, 1999). Heterologous expression of XPR1 either in Nicotiana benthamiana or in mammalian cultured cells showed that it also acts as a Pi exporter (Giovannini et al, 2013;Wege and Poirier, 2014). PHO1 proteins are composed of three distinct regions (Wang et al, 2004).…”

Grapevine and Arabidopsis cation-chloride cotransporters localise to the Golgi and trans-Golgi network and indirectly influence long-distance ion homeostasis and plant salt tolerance

“…Another membrane protein, Arabidopsis thaliana Phosphate1 (AtPHO1), and also, its mammalian homolog, Mus musculus Xenotropic Polytropic Virus Receptor1 (MmXPR1), localize to the plant Golgi and TGN under normal conditions but somehow mediate inorganic phosphate release to the extracellular space (Arpat et al, 2012;Wege and Poirier, 2014). In these studies, it was hypothesized that phosphate export proteins might be present in too low abundance at the PM for detection by fluorophore tagging or alternatively, that phosphate might be loaded into vesicles for exocytosis followed by rapid recycling away from the PM (Arpat et al, 2012;Wege and Poirier, 2014). Iron-regulated transporter1 (IRT1), which mediates iron and divalent metal uptake from the soil by root hairs, was also localized to the TGN and early endosome in Arabidopsis (Barberon et al, 2011).…”