Feedback control of AHR signalling regulates intestinal immunity

The aryl hydrocarbon receptor (AHR) recognizes xenobiotics as well as natural compounds such as tryptophan metabolites, dietary components and microbiota-derived factors, and it is important for maintenance of homeostasis at mucosal surfaces. AHR activation induces cytochrome P4501 (CYP1) enzymes, which oxygenate AHR ligands, leading to their metabolic clearance and detoxification. Thus, CYP1 enzymes have an important feedback role that curtails the duration of AHR signalling, but it remains unclear whether they also regulate AHR ligand availability in vivo. Here we show that dysregulated expression of Cyp1a1 in mice depletes the reservoir of natural AHR ligands, generating a quasi AHR-deficient state. Constitutive expression of Cyp1a1 throughout the body or restricted specifically to intestinal epithelial cells resulted in loss of AHR-dependent type 3 innate lymphoid cells and T helper 17 cells and increased susceptibility to enteric infection. The deleterious effects of excessive AHR ligand degradation on intestinal immune functions could be counter-balanced by increasing the intake of AHR ligands in the diet. Thus, our data indicate that intestinal epithelial cells serve as gatekeepers for the supply of AHR ligands to the host and emphasize the importance of feedback control in modulating AHR pathway activation

Actin waves do not boost neurite outgrowth in the early stages of neuron maturation

During neurite development, Actin Waves (AWs) emerge at the neurite base and move up to its tip, causing a transient retraction of the Growth Cone (GC). Many studies have shown that AWs are linked to outbursts of neurite growth and, therefore, contribute to the fast elongation of the nascent axon. Using long term live cell-imaging, we show that AWs do not boost neurite outgrowth and that neurites without AWs can elongate for several hundred microns. Inhibition of Myosin II abolishes the transient GC retraction and strongly modifies the AWs morphology. Super-resolution nanoscopy shows that Myosin IIB shapes the growth cone-like AWs structure and is differently distributed in AWs and GCs. Interestingly, depletion of membrane cholesterol and inhibition of Rho GTPases decrease AWs frequency and velocity. Our results indicate that Myosin IIB, membrane tension, and small Rho GTPases are important players in the regulation of the AW dynamics. Finally, we suggest a role for AWs in maintaining the GCs active during environmental exploration

Solution processable and optically switchable 1D photonic structures

We report the first demonstration of a solution processable, optically switchable 1D photonic crystal which incorporates phototunable doped metal oxide nanocrystals. The resulting device structure shows a dual optical response with the photonic bandgap covering the visible spectral range and the plasmon resonance of the doped metal oxide the near infrared. By means of a facile photodoping process, we tuned the plasmonic response and switched effectively the optical properties of the photonic crystal, translating the effect from the near infrared to the visible. The ultrafast bandgap pumping induces a signal change in the region of the photonic stopband, with recovery times of several picoseconds, providing a step toward the ultrafast optical switching. Optical modeling uncovers the importance of a complete modeling of the variations of the dielectric function of the photodoped material, including the high frequency region of the Drude response which is responsible for the strong switching in the visible after photodoping. Our device configuration offers unprecedented tunability due to flexibility in device design, covering a wavelength range from the visible to the near infrared. Our findings indicate a new protocol to modify the optical response of photonic devices by optical triggers only

Solution processable and optically switchable 1D photonic structures.

We report the first demonstration of a solution processable, optically switchable 1D photonic crystal which incorporates phototunable doped metal oxide nanocrystals. The resulting device structure shows a dual optical response with the photonic bandgap covering the visible spectral range and the plasmon resonance of the doped metal oxide the near infrared. By means of a facile photodoping process, we tuned the plasmonic response and switched effectively the optical properties of the photonic crystal, translating the effect from the near infrared to the visible. The ultrafast bandgap pumping induces a signal change in the region of the photonic stopband, with recovery times of several picoseconds, providing a step toward the ultrafast optical switching. Optical modeling uncovers the importance of a complete modeling of the variations of the dielectric function of the photodoped material, including the high frequency region of the Drude response which is responsible for the strong switching in the visible after photodoping. Our device configuration offers unprecedented tunability due to flexibility in device design, covering a wavelength range from the visible to the near infrared. Our findings indicate a new protocol to modify the optical response of photonic devices by optical triggers only

Significant microsynteny with new evolutionary highlights is detected between Arabidopsis and legume model plants despite the lack of macrosynteny

The increased amount of data produced by large genome sequencing projects allows scientists to carry out important syntenic studies to a great extent. Detailed genetic maps and entirely or partially sequenced genomes are compared, and macro- and microsyntenic relations can be determined for different species. In our study, the syntenic relationships between key legume plants and two model plants, Arabidopsis thaliana and Populus trichocarpa were investigated. The comparison of the map position of 172 gene-based Medicago sativa markers to the organization of homologous A. thaliana genes could not identify any sign of macrosynteny between the two genomes. A 276 kb long section of chromosome 5 of the model legume Medicago truncatula was used to investigate potential microsynteny with the other legume Lotus japonicus, as well as with Arabidopsis and Populus. Besides the overall correlation found between the legume plants, the comparison revealed several microsyntenic regions in the two more distant plants with significant resemblance. Despite the large phylogenetic distance, clear microsyntenic regions between Medicago and Arabidopsis or Populus were detected unraveling new intragenomic evolutionary relations in Arabidopsis