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Auxin fluctuation and PIN polarization in moss leaf cell reprogramming.
No full textAuxin and its PIN-FORMED (PIN) exporters are essential for tissue repair and regeneration in flowering plants. To gain insight into the evolution of this mechanism, we investigated their roles in leaves excised from Physcomitrium patens, a bryophyte known for its remarkable cell reprogramming capacity. We used various approaches to manipulate auxin levels, including exogenous application, pharmacological manipulations, and auxin biosynthesis mutants. We observed no significant effect on the rate of cell reprogramming. Rather, our analysis of auxin dynamics revealed a decrease in auxin levels upon excision, which was followed by a local increase before the reprogramming process began. Mutant analysis revealed that PpPINs are required for effective cell reprogramming, and endogenously expressed PpPINA-GFP accumulates polarly at sites that will develop into future filamentous stem cells. In addition, hyperpolarized PpPINA variants carrying mutated phosphorylation sites showed a marked delay in reprogramming, whereas endogenous or nonpolar versions do not have this effect. These results underscore that both the levels and the polarity of PpPINA are important for efficient cell reprogramming. Overall, these findings highlight the pivotal role of PIN polarity in plant regeneration. Furthermore, they suggest that understanding polarity mechanisms could have broader implications for improving regenerative processes across various plant species
Keratins coordinate tissue spreading by balancing spreading forces with tissue material properties
No full textFor tissues to spread, they must be deformable while maintaining their structural integrity. How these opposing requirements are balanced within spreading tissues is not yet well understood. Here, we show that keratin intermediate filaments function in epithelial spreading by adapting tissue mechanical resilience to the stresses arising in the tissue during the spreading process. By analysing the expansion of the enveloping cell layer (EVL) over the large yolk cell in early zebrafish embryos in vivo, we found that keratin network maturation in EVL cells is promoted by stresses building up within the spreading tissue. Through genetic interference and tissue rheology experiments, complemented by a vertex model with mechanochemical feedback, we demonstrate that stress-induced keratin network maturation in the EVL increases tissue viscosity, which is essential for preventing tissue rupture. Interestingly, keratins are also required in the yolk cell for mechanosensitive actomyosin network contraction and flow, the force-generating processes pulling the EVL. These dual mechanosensitive functions of keratins enable a balance between pulling force production in the yolk cell and the mechanical resilience of the EVL against stresses generated by these pulling forces, thereby ensuring uniform and robust tissue spreading
TMK-PIN1 drives a short self-organizing circuit for auxin export and signaling in Arabidopsis
No full textThe versatile and pivotal roles of the phytohormone auxin in regulating plant growth and development are typically linked to its directional transport, relying on the polarized PIN-FORMED (PIN) auxin exporters at the plasma membrane (PM). For decades, auxin has been proposed to promote PIN polarization, generating self-regulatory feedback mediating much of plant development, but mechanistic insight into this regulation is lacking. Here, we uncover an auxin-induced protein complex at the PM, containing auxin co-receptors transmembrane kinases (TMKs) and PIN1 auxin exporter, as the core machinery that underlies this feedback regulation. Auxin promotes PIN1 phosphorylation by TMKs, modulating PIN1 polarization and transport activity. We also provide evidence that PIN1-exported extracellular auxin is crucial for TMK activation and cell elongation, thus forming the simplest two-element self-regulatory feedback circuit. Thus, these findings offer direct mechanistic insights into a potential self-organizing circuit for auxin signaling and transport to ensure proper plant development in Arabidopsis
Thiol-Amine complexes for the synthesis and surface engineering of SnTe nanomaterials toward high thermoelectric performance
No full textSnTe has attracted significant research interest as a lead-free alternative to PbTe; however, its intrinsically high hole concentration results in an undesirably low Seebeck coefficient and elevated electronic thermal conductivity, thus significantly limiting its thermoelectric (TE) performance. Herein, we present a cost-effective, binary thiol-amine-mediated colloidal synthesis method to synthesize Bi-doped SnTe nanoparticles, eliminating the use of tri-n-octylphosphine-based precursors. The introduction of an electron-rich Bi dopant reduces the hole concentration and increases the Seebeck coefficient. Furthermore, post-synthetic surface treatment with chalcogenidocadmate complexes promotes atomic interdiffusion during annealing and consolidation, leading to compositional redistribution and modulation of the electronic band structure. Density functional theory (DFT) calculations reveal that co-modification via Bi doping and CdSe-derived chalcogen incorporation reduces the energy offset at the valence band maxima from 0.30 eV to 0.10 eV, thereby enhancing valence band degeneracy. The synergistic structural and electronic band structure modulations produce an SnTe-based material with a record high power factor of 2.1 mW m–1 K–2 at 900 K, a maximum TE figure of merit (zT) of 1.2, and a promising theoretical conversion efficiency of 8.3%. This study reports a versatile and scalable colloidal synthesis strategy that integrates hierarchical structural modulation with electronic band engineering, offering a synergistic route to significantly enhance the TE performance
Triples as links between binary Black Hole mergers, their electromagnetic counterparts, and galactic Black Holes
No full textWe propose a formation pathway linking black holes (BHs) observed in gravitational-wave (GW) mergers, wide BH–stellar systems uncovered by Gaia, and accreting low-mass X-ray binaries (LMXBs). In this scenario, a stellar-mass BH binary undergoes isolated binary evolution and merges while hosting a distant, dynamically unimportant tertiary stellar companion. The tertiary becomes relevant only after the merger, when the remnant BH receives a GW recoil kick. Depending on the kick velocity and system configuration, the outcome can be: (1) a bright electromagnetic (EM) counterpart to the GW merger; (2) an LMXB; (3) a wide BH–stellar companion system resembling the Gaia BH population; or (4) an unbound isolated BH. Modeling the three-body dynamics, we find that ∼0.02% of LIGO–Virgo–KAGRA (LVK) mergers may be followed by an EM counterpart within ∼10 days, produced by tidal disruption of the star by the BH. The flare is likely brightest in the optical–UV and lasts for days to weeks; in some cases, partial disruption causes recurring flares with a period of ∼2 months. We further estimate that this channel can produce ∼1%–10% of Gaia BH systems in the Milky Way. This scenario provides the first physically motivated link between GW sources, Gaia BHs, and some X-ray binaries, and predicts a rare but robust pathway for EM counterparts to binary BH mergers, potentially detectable in LVK’s O5 run
Moist convection and radiative cooling: Dynamical response and scaling
No full textMoist convection is a fundamental process occurring in the Earth's atmosphere. It plays a central role in the weather and climate of the Tropics, where, to first order, the heating of the atmosphere by convection is in balance with the cooling of the atmosphere by the emission of radiation to outer space. In this study, we use a cloud-resolving model in radiative–convective equilibrium with an imposed constant rate of radiative cooling and study the response of moist convection to varying this rate of radiative cooling. In particular, we study two types of simulation: varying air temperature (VAT) simulations, where the air temperature is allowed to adjust to the imposed radiative cooling, and constant air temperature (CAT) simulations, where the surface temperature is tuned to ensure that the atmospheric temperature profile in the domain is constant. We recover the previously known result that, in response to increasing radiative cooling, the area of convection expands rapidly, while the intensity of convection does not change. We find that this response is explained by the increased boundary-layer variability in simulations with greater radiative cooling, which compensates for the decreasing temperature by adding a larger initial velocity close to the cloud base. We also propose a fundamental scaling of the non-dimensional cumulus mass flux in moist convection, which is robust across models of different complexity. We aim to bridge the gap between highly idealised prototypes of moist convection, such as the “Rainy–Bénard convection” introduced by Vallis et al., and comprehensive cloud-resolving models
Escape fractions from unattenuated Lyα emitters around luminous z > 6 quasars
No full textIonized proximity zones around luminous quasars provide a unique laboratory to characterize the Lyα emission lines from z > 6 galaxies without significant attenuation from the intergalactic medium (IGM). However, Lyα line measurements for galaxies within high-redshift quasars’ proximity zones have been rare so far. Here we present deep spectroscopic observations obtained with the NIRSpec/Micro-Shutter Assembly (MSA) instrument on the James Webb Space Telescope of galaxies in two z > 6 quasar fields. We measure the Lyα line fluxes for 50 galaxies at 6 < z < 7 with UV absolute magnitude M UV < −19 (median M UV = −19.97), among which 15 are located near the luminous quasars, i.e., within Δv < 2500 km s−1. We find that galaxies near the quasars show significant flux blueward of the systemic Lyα wavelength, and have higher Lyα equivalent width compared to galaxies at similar redshifts that are not located within the quasars’ environment. Our result indicates little or no redshift evolution for the Lyα emitter fraction from z ∼ 6.4 to z ∼ 5. Leveraging the low IGM opacity in the quasars’ vicinity, we evaluate the Lyα escape fraction (f esc Ly α) of high-redshift galaxies. Our analysis suggests that galaxies at 〈z〉 ≈ 6.4 have an average f esc Ly α = 0.14 ± 0.04. This value is consistent with reionization models where the Lyman continuum escape fraction is low ( fescLyC ≲ 0.1 ) for luminous galaxies, and where the most luminous galaxies have only a minor contribution to the total ionizing photon budget. © 2025. The Author(s). Published by the American Astronomical Society
What determines the maximum mass of AGN-assisted black hole mergers?
No full textThe origin of merging binary black holes detected through gravitational waves remains a fundamental question in astrophysics. While stellar evolution imposes an upper mass limit of ∼50⊙ for black holes, some observed mergers—most notably GW190521—involve significantly more massive components, suggesting alternative formation channels. Here we investigate the maximum masses attainable by black hole mergers within active galactic nucleus (AGN) disks. Using a comprehensive semianalytic model incorporating 27 binary and environmental parameters, we explore the role of AGN disk conditions in shaping the upper end of the black hole mass spectrum. We find that an AGN disk lifetime is the dominant factor, with high-mass mergers (≳200⊙) only possible if disks persist for ≳40 Myr. The joint electromagnetic observation of an AGN-assisted merger could therefore lead to a direct measurement of the age of an AGN disk
Fueling the mind: Brain metabolism in health and neurodevelopmental disorders
No full textThe adult human brain, under resting conditions, consumes approximately 20% of total body glucose, a demand that is even higher during the first decade of life. The brain metabolic landscape is intricately regulated throughout development, and each cell type exhibits distinct metabolic signatures at each specific stage. This picture becomes even more intricate when considering that metabolism is dynamically modulated to sustain critical biological processes, such as cell proliferation and differentiation and synaptic activity–dependent processes. The orchestration between metabolic regulation and the aforementioned physiological processes often relies on metabolism-dependent changes in the epigenetic landscape, which shape gene expression patterns to trigger selected downstream biological responses. Perturbations of brain metabolic pathways are frequently the cause of severe neurodevelopmental disorders. This review explores the latest insights into the regulation of brain metabolism in health and disease