The oxidation of methyl α-D-glucopyranoside with methyl sulproxide and acetic anhydride

The relative proportions of carbonyl, O-acetyl, and O-(methylthio)methylsugars resulting from the partial oxidation of methyl α-D-glucopyranoside with methyl sulphoxide and acetic anhydride have been investigated@ the preparation of the 2- and 6-(methylthio)methyl ethers of methyl α-D-glucopyranoside is described.     

Domestication‐related variation in social preferences in chickens is affected by genotype on a growth QTL

A growth‐related QTL on chicken chromosome 1 has previously been shown to influence domestication behaviour in chickens. In this study, we used Red Junglefowl (RJF) and White Leghorn (WL) as well as the intercross between them to investigate whether stress affects the way birds allocate their time between familiar and unfamiliar conspecifics in a social preference test (‘social support seeking’), and how this is related to genotype at specific loci within the growth QTL. Red Junglefowl males spent more time with unfamiliar chickens before the stressful event compared to the other birds, whereas all birds except WL males tended to spend less time with unfamiliar ones after stress. A significant QTL locus was found to influence both social preference under undisturbed circumstances and social support seeking. The WL allele at this QTL was associated not only with a preference for unfamiliar individuals but also with a shift towards familiar ones in response to stress (social support seeking). A second, suggestive QTL also affected social support seeking, but in the opposite direction; the WL allele was associated with increased time spent with unfamiliar individuals. The region contains several possible candidate genes, and gene expression analysis of a number of them showed differential expression between RJF and WL of AVPR2 (receptor for vasotocin), and possibly AVPR1a (another vasotocin receptor) and NRCAM (involved in neural development) in the lower frontal lobes of the brains of RJF and WL animals. These three genes continue to be interesting candidates for the observed behavioural effects .     

AtDUR3 encodes a new type of high-affinity urea/H+ symporter in Arabidopsis

Urea is the major nitrogen form supplied as fertilizer in agricultural plant production but also an important nitrogen metabolite in plants. We report the cloning and functional characterization of AtDUR3, a high-affinity urea transporter in plants. AtDUR3 contains 14 putative transmembrane-spanning domains and represents an individual member in Arabidopsis that belongs to a superfamily of sodium-solute symporters. Heterologous expression in urea uptake-defective yeast as well as two-electrode voltage clamp and uptake studies using (14)C-labeled urea in AtDUR3-expressing oocytes demonstrated that AtDUR3 mediates urea transport. In both heterologous systems, urea transport was stimulated at low pH. In oocytes, inward currents indicated that urea is cotransported with protons. By contrast, a supply of Na(+) ions could not stimulate urea transport. Transport of (14)C-labeled urea by AtDUR3 in oocytes exhibited saturation kinetics with a K(m) of approximately 3 micro M. AtDUR3 was expressed in shoots and roots and upregulated during early germination and under nitrogen deficiency in roots. We propose a role of AtDUR3 in urea uptake by plant cells at low external urea concentrations.     

Localized iron supply triggers lateral root elongation in Arabidopsis by altering the AUX1-mediated auxin distribution

Root system architecture depends on nutrient availability, which shapes primary and lateral root development in a nutrient-specific manner. To better understand how nutrient signals are integrated into root developmental programs, we investigated the morphological response of Arabidopsis thaliana roots to iron (Fe). Relative to a homogeneous supply, localized Fe supply in horizontally separated agar plates doubled lateral root length without having a differential effect on lateral root number. In the Fe uptake-defective mutant iron-regulated transporter1 (irt1), lateral root development was severely repressed, but a requirement for IRT1 could be circumvented by Fe application to shoots, indicating that symplastic Fe triggered the local elongation of lateral roots. The Fe-stimulated emergence of lateral root primordia and root cell elongation depended on the rootward auxin stream and was accompanied by a higher activity of the auxin reporter DR5-β-glucuronidase in lateral root apices. A crucial role of the auxin transporter AUXIN RESISTANT1 (AUX1) in Fe-triggered lateral root elongation was indicated by Fe-responsive AUX1 promoter activities in lateral root apices and by the failure of the aux1-T mutant to elongate lateral roots into Fe-enriched agar patches. We conclude that a local symplastic Fe gradient in lateral roots upregulates AUX1 to accumulate auxin in lateral root apices as a prerequisite for lateral root elongation.     

Focus Issue on Roots: Root Nutrient Foraging

During a plant''s lifecycle, the availability of nutrients in the soil is mostly heterogeneous in space and time. Plants are able to adapt to nutrient shortage or localized nutrient availability by altering their root system architecture to efficiently explore soil zones containing the limited nutrient. It has been shown that the deficiency of different nutrients induces root architectural and morphological changes that are, at least to some extent, nutrient specific. Here, we highlight what is known about the importance of individual root system components for nutrient acquisition and how developmental and physiological responses can be coupled to increase nutrient foraging by roots. In addition, we review prominent molecular mechanisms involved in altering the root system in response to local nutrient availability or to the plant''s nutritional status.In natural and agricultural soils, the ability of plants to quickly and efficiently acquire nutrients may determine their competitive success and productivity. Because mineral elements interact differently with themselves and other soil constituents or are carried by water out of the rooted soil volume, their availability to plants may decrease and lead to nutrient deficiency. Under these conditions, plants activate foraging responses that include morphological changes, such as the modulation of root system architecture (RSA) or root hair formation, and physiological changes, such as the release of nutrient-mobilizing root exudates or the expression of nutrient transporters (Gojon et al., 2009; Hinsinger et al., 2009; Gruber et al., 2013). These responses are often spatially coupled to increase the root-soil interaction zone and improve the ability of the plant to intercept immobile nutrients. Noteworthy, although not discussed herein, symbiosis or associative rhizosphere microorganisms can also alter the RSA and enhance the foraging capacity of the plant (Gutjahr and Paszkowski, 2013). Here, we provide an update on the morphological responses induced by plants to forage sparingly available nutrients and some of the underlying molecular mechanisms known to date to be involved in RSA adaptations to nutrient availabilities.     

N-terminal cysteines affect oligomer stability of the allosterically regulated ammonium transporter LeAMT1;1

AMMONIUM TRANSPORTER (AMT) proteins are conserved in all domains of life and mediate the transport of ammonium or ammonia across cell membranes. AMTs form trimers and use intermolecular interaction between subunits to regulate activity. So far, binding forces that stabilize AMT protein complexes are not well characterized. High temperature or reducing agents released mono- and dimeric forms from trimeric complexes formed by AMT1;1 from Arabidopsis and tomato. However, in the paralogue LeAMT1;3, trimeric complexes were not detected. LeAMT1;3 differs from the other AMTs by an unusually short N-terminus, suggesting a role for the N-terminus in oligomer stability. Truncation of the N-terminus in LeAMT1;1 destabilized the trimer and led to loss of functionality when expressed in yeast. Swapping of the N-terminus between LeAMT1;1 and LeAMT1;3 showed that sequences in the N-terminus of LeAMT1;1 are necessary and sufficient for stabilization of the interaction among the subunits. Two N-terminal cysteine residues are highly conserved among AMT1 transporters in plants but are lacking in LeAMT1;3. C3S or C27S variants of LeAMT1;1 showed reduced complex stability, which coincided with lower transport capacity for the substrate analogue methylammonium. Both cysteine-substituted LeAMT1;1 variants showed weaker interactions with the wildtype as determined by a quantitative analysis of the complex stability using the mating-based split-ubiquitin assay. These data indicate that the binding affinity of AMT1 subunits is stabilized by cysteines in the N-terminus and suggest a role for disulphide bridge formation via apoplastic N-terminal cysteine residues.     

A cost-effective high-throughput microcosm system for studying nitrogen dynamics at the plant-microbe-soil interface

Plant and Soil - In the present study a new microcosm system was evaluated for its suitability to investigate nitrogen dynamics between soils, plants and microbes. Five different agricultural soils...