Article

Aquaporin homologues in plants and mammals transport ammonia. FEBS Lett

IT University of Copenhagen, København, Capital Region, Denmark
FEBS Letters (Impact Factor: 3.17). 10/2004; 574(1-3):31-6. DOI: 10.1016/j.febslet.2004.08.004
Source: PubMed

ABSTRACT

Using functional complementation and a yeast mutant deficient in ammonium (NH4+) transport (Deltamep1-3), three wheat (Triticum aestivum) TIP2 aquaporin homologues were isolated that restored the ability of the mutant to grow when 2 mM NH4+ was supplied as the sole nitrogen source. When expressed in Xenopus oocytes, TaTIP2;1 increased the uptake of NH4+ analogues methylammonium and formamide. Furthermore, expression of TaTIP2;1 increased acidification of the oocyte-bathing medium containing NH4+ in accordance with NH3 diffusion through the aquaporin. Homology modeling of TaTIP2;1 in combination with site directed mutagenesis suggested a new subgroup of NH3-transporting aquaporins here called aquaammoniaporins. Mammalian AQP8 sharing the aquaammoniaporin signature also complemented NH4+ transport deficiency in yeast.

Download full-text

Full-text

Available from: Dan Arne Klaerke
  • Source
    • "Major Intrinsic Proteins (MIPs) (Agre et al., 1993;Maurel, 1997;Gomes et al., 2009).Liu et al., 2003;Uehlein et al., 2003;Jahn et al., 2004;Bienert et al., 2007;Bienert et al., 97 2008;Bienert et al., 2011;Bienert et al., 2014). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Aquaporins (AQPs) are water channels allowing fast and passive diffusion of water across cell membranes. It was hypothesized that AQPs contribute to cell elongation processes by allowing water influx across the plasma membrane and the tonoplast in order to maintain adequate turgor pressure. Here, we report that, in Arabidopsis thaliana, the highly abundant tonoplast AQP isoforms AtTIP1;1, AtTIP1;2 and AtTIP2;1 facilitate the emergence of new lateral root primordia (LRP). The number of lateral roots was strongly reduced in the triple tip mutant, whereas the single, double and triple tip mutants showed no or minor reduction in growth of the main root. This phenotype was due to the retardation of LRP emergence. Live cell imaging revealed that tight spatio-temporal control of TIP abundance in the tonoplast of the different LRP cells is pivotal to mediating this developmental process. While lateral root emergence is correlated to a reduction of AtTIP1;1 and AtTIP1;2 protein levels in LRPs, expression of AtTIP2;1 is specifically needed in a restricted cell population at the base, then later at the flanks, of developing LRPs. Interestingly, the LRP emergence phenotype of the triple tip mutants could be fully rescued by expressing AtTIP2;1 under its native promoter. We conclude that TIP isoforms allow the spatial and temporal fine-tuning of cellular water transport which is critically required during the highly regulated process of LRP morphogenesis and emergence.
    Full-text · Article · Jan 2016 · Plant physiology
  • Source
    • "It is proposed that the interaction with GS creates a metabolic channel to aid assimilation of fixed nitrogen and prevent futile cycling of ammonia (Masalkar et al., 2010). It is interesting to note that other members of the superfamily, such as Arabidopsis tonoplast intrinsic protein (TIP) family, and mammalian AQP1 and AQP8 also transport ammonia (Jahn et al., 2004; Loqué et al., 2005; Zeuthen et al., 2009). Earlier studies on Nodulin 26 suggested that Nodulin 26 has high permeability to water and also transports glycerols and formamide (Dean et al., 1999; Guenther et al., 2003; Rivers et al., 1997), and that its permeability may be regulated by phosphorylation (Weaver and Roberts, 1992). "
    [Show abstract] [Hide abstract]
    ABSTRACT: During establishment of the legume–rhizobia symbiosis and the formation of nitrogen-fixing nodules, interactions between the symbiotic partners result in the formation of a large number of organelle-like structures, called symbiosomes, inside infected cells of the root nodule. The symbiosome is the fundamental cellular unit of symbiotic nitrogen fixation, in which the plant provides carbon and other essential nutrients to the bacteroid to support nitrogen fixation and bacteroid metabolism, and the bacteroid provides fixed N to the plant. In this review, particular emphasis is given to symbiosome formation and the identification of transporters on the symbiosome membrane (SM) that are responsible for metabolite or nutrient transport across the SM.
    Full-text · Chapter · Jul 2015
  • Source
    • "Even neutral , protonated arsenous (Liu et al., 2002; Wu et al., 2010) and silicic acid (Ma et al., 2006) have been found to pass. Further substrates of AQPs are solubilized gasses, namely ammonia (Jahn et al., 2004; Zeuthen et al., 2006) and carbon dioxide (Nakhoul et al., 1998). Especially the latter has been linked to permeation through the central pore (Musa-Aziz et al., 2009). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Classically, aquaporins are divided based on pore selectivity into water specific, orthodox aquaporins and solute-facilitating aquaglyceroporins, which conduct, e.g., glycerol and urea. However, more aquaporin-passing substrates have been identified over the years, such as the gasses ammonia and carbon dioxide or the water-related hydrogen peroxide. It became apparent that not all aquaporins clearly fit into one of only two subfamilies. Furthermore, certain aquaporins from both major subfamilies have been reported to conduct inorganic anions, such as chloride, or monoacids/monocarboxylates, such as lactic acid/lactate. Here, we summarize the findings on aquaporin anion transport, analyze the pore layout of such aquaporins in comparison to prototypical non-selective anion channels, monocarboxylate transporters, and formate-nitrite transporters. Finally, we discuss in which scenarios anion conducting aquaporins may be of physiological relevance.
    Full-text · Article · Sep 2014 · Frontiers in Pharmacology
Show more