, 2005). PHA production appears to be an important trait for root colonization and plant growth promotion by azospirilla. Plant growth promotion effects are more consistent with A. brasilense inoculants containing cells with high amounts of PHA. For instance, field experiments carried out in South America with maize and wheat revealed that increased crop yields were consistently obtained using inoculants prepared with PHA-rich Azospirillum cells (Dobbelaere et al., 2001; Helman et al., 2011; Table 3). Carotenoids are tetraterpenoid click here organic pigments that occur in

plants and in some bacteria and fungi. In bacteria, carotenoids counteract photo-oxidative Selleckchem Enzalutamide damage (Krinsky, 1979). They are known to quench singlet oxygen and to have chain-breaking ability in radical-mediated autoxidation reactions (Burton & Ingold, 1984; Ziegelhoffer & Donohue, 2009). Many azospirilla produce carotenoids (Fig. 3), and

30 years ago, Nur et al. (1981) suggested that in this bacterium, carotenoids play an important role in protecting nitrogenase against oxidative damage, thus being critical for nitrogen fixation under nitrogen-deficient conditions. This hypothesis was confirmed by comparative studies using A. brasilense strains producing different levels of carotenoids (Hartmann & Hurek, 1988; Baldani et al., 2005). Bacteria that live in the rhizosphere experience variations in temperature, Gemcitabine concentration salinity, osmolarity, pH, and availability of nutrients and oxygen (Zahran, 1999). In response to specific stimuli, bacterial sigma factors alter the pattern of gene expression by changing the affinity and specificity of RNA polymerase to different promoters during initiation of transcription (Heimann, 2002). Among the different sigma factors, group 4 s70 sigma factors were initially thought to be involved in responses to changes in the extra-cytoplasmic compartment of the cell and hence were

called extracytoplasmic function (ECF) sigma factors (Heimann, 2002). In the case of rhizosphere bacteria, it is assumed that these sigma factors are critical in adaptation, survival, and proliferation in the soil, particularly under stressful conditions. The involvement of the ECF sigma factor RpoE (also known as σE) in regulation of carotenoid synthesis in A. brasilense as well as in its tolerance to abiotic stresses was recently investigated by Mishra et al. (2011). An in-frame rpoE deletion mutant of A. brasilense Sp7 was carotenoidless and slow-growing, and was more sensitive than the wild type to salt, ethanol, and methylene blue stresses. Expression of rpoE in the rpoE deletion mutant complemented the defects in growth, carotenoid biosynthesis, and sensitivity to the different stresses (Mishra et al., 2011).

They also, near uniquely, express presynaptic cannabinoid type 1 receptors (CB1R). CB1R activation and CCK both decrease the inhibition produced by these interneurones (Katona et al., 1999; Hájos http://www.selleckchem.com/products/PD-98059.html et al., 2000; Neu et al., 2007; Freund, 2003 for review) and both CCK analogues and cannabis are reported to induce panic attacks, whereas increasing the release

of 5-HT, which activates these interneurones, reduces the attacks. These interneurones and the α2-GABAARs they innervate would therefore appear ideally placed to control anxiety. Indeed, enhancement only of the inhibition mediated by α2/3-GABAARs reduces behavioural indices of anxiety (Möhler et al., 2002; McKernan et al., 2000; Whiting, 2006). The potential, therefore, for nonsedative anxiolytic therapies with reduced tolerance and withdrawal and for selective partial agonists as anticonvulsants with reduced dependence is driving development of new benzodiazepine

site ligands. The α5-GABAARs that are activated by dendrite-preferring interneurones in cortical regions do not appear to contribute to the sedative or anxiolytic Neratinib mw effects of benzodiazepines. This is, perhaps, not surprising when it is remembered that these receptors are activated by very different types of interneurones. Disrupting or blocking these α5-GABAARs enhanced cognitive performance in rats in hippocampal-dependent learning tasks (Collinson et al., 2002; Chambers et al., 2003, 2004), with α5-GABAARs being implicated as control elements of the temporal association of threat cues in trace fear conditioning (Crestani et al., 2002). Moreover, selective blockade of these receptors in people has been reported to block alcohol’s amnestic effect (Nutt et al., 2007). Interest in partial α5-GABAAR inverse agonists as cognitive enhancers is therefore growing. Clearly, if these different GABAAR subtypes were randomly distributed over the synaptic and extrasynaptic regions of their postsynaptic

targets, the very specific effects on behaviour and cognition that enhancing or disrupting their activity has, would simply not be possible. selleck screening library Why there is such specificity remains to be determined, as it would be unreasonable to propose that it is designed to allow the development of anxiolytic and cognitive-enhancing drugs, convenient though this may prove. It may be that elusive endogenous benzodiazepine site ligands do indeed exist and are able to modulate these GABAARs differentially. That this is at least a possibility is indicated by the partial inverse agonist activity, at synaptic receptors in situ (File et al., 1986; King et al., 1985; Thomson et al., 2000), of benzodiazepine site ligands that act as pure antagonists in expression systems.