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Boron (B) in soil is taken up by roots through NIP5;1, a boric acid channel, and is loaded into the xylem by BOR1, a borate exporter. Here, the function of Arabidopsis thaliana NIP6;1, the most similar gene to NIP5;1, was studied. NIP6;1 facilitates the rapid permeation of boric acid across the membrane but is completely impermeable to water. NIP6;1 transcript accumulation is elevated in response to B deprivation in shoots but not in roots. NIP6;1 promoter–β-glucuronidase is predominantly expressed in nodal regions of shoots, especially the phloem region of vascular tissues. Three independently identified T-DNA insertion lines for the NIP6;1 gene exhibited reduced expansion of young rosette leaves only under low-B conditions. B concentrations are reduced in young rosette leaves but not in the old leaves of these mutants. Taken together, these data strongly suggest that NIP6;1 is a boric acid channel required for proper distribution of boric acid, particularly among young developing shoot tissues. We propose that NIP6;1 is involved in xylem–phloem transfer of boric acid at the nodal regions and that the water-tight property of NIP6;1 is important for this function. It is proposed that during evolution, NIP5;1 and NIP6;1 were diversified in terms of both the specificity of their expression in plant tissues and their water permeation properties, while maintaining their ability to be induced under low B and their boric acid transport activities.

Major intrinsic proteins (MIPs) are a family of membrane channels that facilitate the bidirectional transport of water and small uncharged solutes such as glycerol. The 35 full-length members of the MIP family in Arabidopsis are segregated into four structurally homologous subfamilies: plasma membrane intrinsic proteins (PIPs), tonoplast intrinsic proteins (TIPs), nodulin 26-like intrinsic membrane proteins (NIPs), and small basic intrinsic proteins (SIPs). Computational methods were used to construct structural models of the putative pore regions of various plant MIPs based on homology modeling with the atomic resolution crystal structures of mammalian aquaporin 1 and the bacterial glycerol permease GlpF. Based on comparisons of the narrow selectivity filter regions (the aromatic/Arg [ar/R] filter), the members of the four phylogenetic subfamilies of Arabidopsis MIPs can be classified into eight groups. PIPs possess a uniform ar/R signature characteristic of high water transport aquaporins, whereas TIPs are highly diverse with three separate conserved ar/R regions. NIPs possess two separate conserved ar/R regions, one that is similar to the archetype, soybean (Glycine max) nodulin 26, and another that is characteristic of Arabidopsis NIP6;1. The SIP subfamily possesses two ar/R subgroups, characteristic of either SIP1 or SIP2. Both SIP ar/R residues are divergent from all other MIPs in plants and other kingdoms. Overall, these findings suggest that higher plant MIPs have a common fold but show distinct differences in proposed pore apertures, potential to form hydrogen bonds with transported molecules, and amphiphilicity that likely results in divergent transport selectivities.Members of the major intrinsic protein (MIP) family form a large and diverse group of membrane proteins that facilitate the bidirectional transport of water and some small solutes across cellular membranes (Agre et al., 2002;Thomas et al., 2002). MIPs are widely distributed in organisms from bacteria to higher eukaryotes, and these proteins are especially abundant in plants, with 35 full-length genes present in Arabidopsis (Johanson et al., 2001;Quigley et al., 2001). Members of the plant MIP family have been implicated in cell elongation and development, changes in hydraulic conductivity in response to environmental cues, and numerous other processes that require rapid transmembrane movements of water (for review, see Johansson et al., 2000;Maurel et al., 2002;Tyerman et al., 2002).MIP family members in Arabidopsis are subdivided into four subfamilies: the plasma membrane intrinsic proteins (PIPs; 13 genes), the tonoplast intrinsic membrane proteins (TIPs; 10 genes), the nodulin 26-like intrinsic membrane proteins (NIPs; 9 genes), and the small basic intrinsic proteins (SIPs; 3 genes) (Weig et al., 1997;Johanson et al., 2001;Quigley et al., 2001). By contrast, mammals have only two functional subfamilies of MIPs: water-specific aquaporins and solute-transporting glyceroporins and aquaglyceroporins (Agre et al., 2002). This disparity leads...

Soybean nodulin 26 is expressed and targeted to the symbiosome membrane of nitrogen-fixing nodules, where it forms an aquaporin channel with a modest water transport rate. In this study, we show that the phosphorylation of nodulin 26 on Ser-262, which is catalyzed by a symbiosome membrane-associated calcium-dependent protein kinase, stimulates its intrinsic water transport rate. Furthermore, using a phosphospecific antibody, we have elucidated the developmental appearance and regulation of nodulin 26 phosphorylation in vivo. Although nodulin 26 protein is detected first in differentiating infected cells (16 days), phosphorylated nodulin 26 does not become pronounced until infected cell maturation (25 days). Phosphorylation is sustained at steady state levels until entry into senescence. Nodulin 26 phosphorylation is enhanced further by osmotic stresses (water deprivation and salinity). Thus, the phosphorylation of nodulin 26 coincides with the establishment of mature nitrogen-fixing symbiosomes, is regulated by osmotic stresses that induce calcium-signaling pathways, and appears to be part of the adaptive responses of infected cells to osmotic challenge.

FLSs are cost-effective for the prevention of further fractures in fragility-fracture patients. The cost of widespread adoption of FLS across the UK is small in comparison with other service provision and would be expected to result in important benefits in fractures avoided and reduced hospital bed occupancy.

Mind wandering is a pervasive threat to transportation safety, potentially accounting for a substantial number of crashes and fatalities. In the current study, mind wandering was induced through completion of the same task for 5 days, consisting of a 20-min monotonous freeway-driving scenario, a cognitive depletion task, and a repetition of the 20-min driving scenario driven in the reverse direction. Participants were periodically probed with auditory tones to self-report whether they were mind wandering or focused on the driving task. Self-reported mind wandering frequency was high, and did not statistically change over days of participation. For measures of driving performance, participant labeled periods of mind wandering were associated with reduced speed and reduced lane variability, in comparison to periods of on task performance. For measures of electrophysiology, periods of mind wandering were associated with increased power in the alpha band of the electroencephalogram (EEG), as well as a reduction in the magnitude of the P3a component of the event related potential (ERP) in response to the auditory probe. Results support that mind wandering has an impact on driving performance and the associated change in driver’s attentional state is detectable in underlying brain physiology. Further, results suggest that detecting the internal cognitive state of humans is possible in a continuous task such as automobile driving. Identifying periods of likely mind wandering could serve as a useful research tool for assessment of driver attention, and could potentially lead to future in-vehicle safety countermeasures.

A strategy for elucidating specific molecular targets of calcium and calmodulin in plant defense responses has been developed. We have used a dominant‐acting calmodulin mutant (VU‐3, Lys to Arg115) to investigate the oxidative burst and nicotinamide co‐enzyme fluxes after various stimuli (cellulase, harpin, incompatible bacteria, osmotic and mechanical) that elicit plant defense responses in transgenic tobacco cell cultures. VU‐3 calmodulin differs from endogenous plant calmodulin in that it cannot be methylated post‐translationally, and as a result it hyperactivates calmodulin‐dependent NAD kinase. Cells expressing VU‐3 calmodulin exhibited a stronger active oxygen burst that occurred more rapidly than in normal control cells challenged with the same stimuli. Increases in NADPH level were also greater in VU‐3 cells and coincided both in timing and magnitude with development of the active oxygen species (AOS) burst. These data show that calmodulin is a target of calcium fluxes in response to elicitor or environmental stress, and provide the first evidence that plant NAD kinase may be a downstream target which potentiates AOS production by altering NAD(H)/NADP(H) homeostasis.