Central-cell-produced attractants control fertilization recovery.

Animal fertilization relies on hundreds of sperm racing toward the egg, whereas, in angiosperms, only two sperm cells are delivered by a pollen tube to the female gametes (egg cell and central cell) for double fertilization. However, unsuccessful fertilization under this one-pollen-tube design can be detrimental to seed production and plant survival. To mitigate this risk, unfertilized-gamete-controlled extra pollen tube entry has been evolved to bring more sperm cells and salvage fertilization. Despite its importance, the underlying molecular mechanism of this phenomenon remains unclear. In this study, we report that, in Arabidopsis, the central cell secretes peptides SALVAGER1 and SALVAGER2 in a directional manner to attract pollen tubes when the synergid-dependent attraction fails or is terminated by pollen tubes carrying infertile sperm cells. Moreover, loss of SALs impairs the fertilization recovery capacity of the ovules. Therefore, this research uncovers a female gamete-attraction system that salvages seed production for reproductive assurance.

Targeting senescent HDF with the USP7 inhibitor P5091 to enhance DFU wound healing through the p53 pathway.

OBJECTIVE: The objective of this study was to examine the potential of USP7 as a target for senolytic therapy and to investigate the molecular mechanism by which its inhibitor selectively induced apoptosis in senescent HDF and enhanced DFU wound healing. METHODS: Clinical samples of DFU were collected to detect the expression of USP7 and aging-related proteins using immunohistochemistry and Western blot. In addition, ß-galactosidase staining, qPCR, flow cytometry, ROS and MMP kits, and Western blot were used to analyze the biological functions of P5091 on senescence, cycle, and apoptosis. RNAseq was employed to further analyze the molecular mechanism of P5091. Finally, the DFU rat model was established to evaluate the effect of P5091 on wound healing. RESULTS: The expression of USP7 and p21 were increased in DFU clinical samples. After treatment with d-glucose (30 mM, 7 days), ß-galactosidase staining was deepened, proliferation rate decreased. USP7 inhibitors (P5091) could reduce the release of SASP factors, activate the production of ROS, and reduce MMP. In addition, it induced apoptosis and selectively clears senescent cells through the p53 signaling pathway. Finally, P5091 can improve diabetic wound healing in rats. CONCLUSION: This study clarified the molecular mechanism of USP7 inhibitor (P5091) selectively inducing apoptosis of high glucose senescent HDF cells. This provides a new senolytics target and experimental basis for promoting DFU wound healing.

Angle-insensitive topological interface states in hybrid one-dimensional photonic crystal heterostructures containing all-dielectric metamaterials.

Topological interface states (TISs) in conventional one-dimensional (1D) photonic crystal (PhC) heterostructures strongly shift toward higher frequencies as the incident angle increases. This strong blueshift property of TISs intensively limits the operating angle ranges of TISs. Herein, we design two angle-insensitive photonic bandgaps (PBGs) in two hybrid 1D PhCs containing all-dielectric metamaterials. By cascading these two hybrid 1D PhCs to construct a hybrid 1D PhC heterostructure, we achieve an angle-insensitive TIS under transverse magnetic polarization. Empowered by the angle-insensitive property of the PBGs, the angular tolerance of the TIS reaches 69.65°, which is much higher than those of the TISs in conventional 1D PhC heterostructures. In addition, the angle-insensitive property of the TIS is robust against the layer thickness. Our work provides a viable route to achieving TISs with high angular tolerances and would facilitate the applications of photonic topological states.

Topological plasmons in stacked graphene nanoribbons.

In this Letter, we theoretically study the topological plasmons in Su-Schrieffer-Heeger (SSH) model-based graphene nanoribbon (GNR) layers. We find that for the one-dimensional (1D) stacked case, only two topological modes with the field localized in the top or bottom layer are predicted to exist by the Zak phase. When we further expand the stacked 1D GNR layers to two-dimensional (2D) arrays in the in-plane direction, the topology is then characterized by the 2D Zak phase, which predicts the emergence of three kinds of topological modes: topological edge, surface, and corner modes. For a 2D ribbon array with Nx × Ny units, there are 4(Ny - 1), 4(Nx - 1), and 4 topological edge, surface, and corner modes, and the field is highly localized at the edge/surface/corner ribbons. This work offers a platform to realize topological modes in GNRs and could be important for the design of topological photonic devices such as lasers and sensors.

Dual-mode tunable absorber based on quasi-bound states in the continuum.

In this Letter, we propose a novel, to the best of our knowledge, dual-mode tunable absorber that utilizes quasi-bound states in the continuum (q-BIC) based on the periodically arranged silicon cylinders tetramer. By introducing asymmetry perturbation through manipulating the diameters of diagonal cylinders in the all-dielectric structure, the symmetry-protected BIC (SP-BIC) transforms into q-BIC, leading to the emergence of one transmission and one reflection Fano-like resonant mode. The relationship between the quality factor of each mode and the asymmetry parameter α is analyzed, revealing an exponential dependence with an exponent of -1.75, i.e., Q ∝ α-1.75. To explain the underlying physics, multipole decomposition analysis and Aleksandra's theory are applied. Subsequently, a monolayer graphene is introduced to the all-dielectric structure to demonstrate the application of the dual-mode tunable absorber. When the critical coupling condition is satisfied, each mode can achieve the theoretical maximum absorption, demonstrating the distinctive capability of our proposed absorber for tuning and efficient light absorption. This research provides valuable insights into light-matter interactions and opens up possibilities for optical modulation and the development of graphene-based devices.

Correction: A redshifted photonic bandgap and wide-angle polarization selection in an all-hyperbolic-metamaterial one-dimensional photonic crystal.

Correction for 'A redshifted photonic bandgap and wide-angle polarization selection in an all-hyperbolic-metamaterial one-dimensional photonic crystal' by Feng Wu et al., Phys. Chem. Chem. Phys., 2023, 25, 10785-10794, https://doi.org/10.1039/D3CP00280B.

A redshifted photonic bandgap and wide-angle polarization selection in an all-hyperbolic-metamaterial one-dimensional photonic crystal.

According to the Bragg scattering theory, photonic bandgaps (PBGs) in all-dielectric one-dimensional (1-D) photonic crystals (PhCs) are polarization-insensitive. This polarization-insensitive property of PBGs poses a challenge in wide-angle high-performance polarization selection. Herein, we theoretically investigate the angle dependence of the PBGs in a novel kind of 1-D PhC called all-hyperbolic-metamaterial (all-HMM) 1-D PhC entirely composed of HMMs. As the incident angle increases, the PBGs in all-HMM 1-D PhCs exhibit the redshift property under transverse magnetic polarization while exhibiting the blueshift property under transverse electric polarization. Empowered by the polarization-sensitive property of the PBGs, wide-angle high-performance polarization selection can be theoretically achieved. Such a wide-angle polarizer would be useful in liquid crystal displays, quantum interferometers, and Q-switched lasers.

A dual-band hydrogen sensor based on Tamm plasmon polaritons.

Optical hydrogen sensors possess significant potential in various fields, including aerospace and fuel cell applications, which is due to their compact design and immunity to electromagnetic interference. However, commonly used sensors mostly use single-band sensing, which increases the risk of inaccurate measurements due to environmental interference or operational errors. To address this issue, this study proposes a dual-band hydrogen sensor comprising a Pd metal layer, a dielectric spacer layer, a defect layer, and a photonic crystal. By leveraging the interaction between the defect mode in the excitonic microcavity structure and the Tamm plasmon polaritons (TPPs) and Fabry-Perot (FP) resonances, the structure simultaneously generates two near-zero resonance valleys in the visible wavelength range. By adjusting the thickness of the defect layer, the coupling effect of the defect mode and TPPs together with FP resonance respectively is optimized. When the thickness is 0.27 µm, the sensitivities of the Tamm resonance band and FP resonance band are 239 and 21 RIU-1, respectively. Compared with the common sensors with a single band, its low-sensitivity wavelength can be used as a reference to assist the high-sensitivity wavelength for sensing. In addition, we find that the proposed sensor, through calculation, has good fault tolerance for both the thickness of the defect layer and the incident light angle. This study demonstrates a dual-band hydrogen sensor with TPPs, which is important for exploring new optical hydrogen sensors.

Ginkgo Biflavones Cause p53 Wild-Type Dependent Cell Death in a Transcription-Independent Manner of p53.

Ginkgo biloba, as a medicinal plant in both traditional and western medicine, emerged as a potential therapeutic agent for the management of a variety of diseases, but ginkgo biflavones (bilobetin, isoginkgetin, and ginkgetin) application in cancer therapy and underlying mechanisms of action remained elusive. In the present study, we identified ginkgo biflavones as potential p53 activators that could enhance p53 protein expression level by inhibiting MDM2 protein expression. At the same time, they induced cell death independent of p53 transcriptional activity. Moreover, ginkgetin was a standout among ginkgo biflavones that reduced the survival of HCT-116 cells by induction of apoptosis and G2/M phase arrest. Furthermore, ginkgo biflavones induced ROS generation significantly, which resulted in ferroptosis. Finally, we provide evidence that ginkgetin strengthened the antitumor effect of fluorouracil (5-FU) in the HCT-116 colon cancer xenograft model. To sum up, ginkgo biflavones represent a new class of p53 activator that depends on the p53 wild-type status and warrants further exploration as potential anticancer agents.

Transcriptional repression specifies the central cell for double fertilization.

Double fertilization is a key innovation for the evolutionary success of angiosperms by which the two fertilized female gametes, the egg cell and central cell, generate the embryo and endosperm, respectively. The female gametophyte (embryo sac) enclosed in the sporophyte is derived from a one-celled haploid cell lineage. It undergoes successive events of mitotic divisions, cellularization, and cell specification to give rise to the mature embryo sac, which contains the two female gametes accompanied by two types of accessory cells, namely synergids and antipodals. How the cell fate of the central cell is specified has long been equivocal and is further complicated by the structural diversity of female gametophyte across plant taxa. Here, MADS-box protein AGL80 was verified as a transcriptional repressor that directly suppresses the expression of accessory cell-specific genes to specify the central cell. Further genetic rescue and phylogenetic assay of the AGL80 orthologs revealed a possible conserved mechanism in the Brassicaceae family. Results from this study provide insight into the molecular determination of the second female gamete cell in Brassicaceae.

Ultra-sensitive refractive index sensing enabled by a dramatic ellipsometric phase change at the band edge in a one-dimensional photonic crystal.

Surface plasmon polaritons (SPPs) and Bloch surface waves (BSWs) have been widely utilized to design sensitive refractive index sensors. However, SPP- and BSW-based refractive index sensors require additional coupling component (prism) or coupling structure (grating or fiber), which increases the difficulty to observe ultra-sensitive refractive index sensing in experiments. Herein, we realize dramatic ellipsometric phase change at the band edges in an all-dielectric one-dimensional photonic crystal for oblique incidence. By virtue of the dramatic ellipsometric phase change at the long-wavelength band edge, we design an ultra-sensitive refractive index sensor at near-infrared wavelengths. The minimal resolution of the designed sensor reaches 9.28×10-8 RIU. Compared with SPP- and BSW-based refractive index sensors, the designed ultra-sensitive refractive index sensor does not require any additional coupling component or coupling structure. Such ultra-sensitive refractive index sensor would possess applications in monitoring temperature, humidity, pressure, and concentration of biological analytes.

A receptor heteromer mediates the male perception of female attractants in plants.

Sexual reproduction requires recognition between the male and female gametes. In flowering plants, the immobile sperms are delivered to the ovule-enclosed female gametophyte by guided pollen tube growth. Although the female gametophyte-secreted peptides have been identified to be the chemotactic attractant to the pollen tube, the male receptor(s) is still unknown. Here we identify a cell-surface receptor heteromer, MDIS1-MIK, on the pollen tube that perceives female attractant LURE1 in Arabidopsis thaliana. MDIS1, MIK1 and MIK2 are plasma-membrane-localized receptor-like kinases with extracellular leucine-rich repeats and an intracellular kinase domain. LURE1 specifically binds the extracellular domains of MDIS1, MIK1 and MIK2, whereas mdis1 and mik1 mik2 mutant pollen tubes respond less sensitively to LURE1. Furthermore, LURE1 triggers dimerization of the receptors and activates the kinase activity of MIK1. Importantly, transformation of AtMDIS1 to the sister species Capsella rubella can partially break down the reproductive isolation barrier. Our findings reveal a new mechanism of the male perception of the female attracting signals.

Broadband wide-angle multilayer absorber based on a broadband omnidirectional optical Tamm state.

Recently, broadband optical Tamm states (OTSs) in heterostructures composed of highly lossy metal layers and all-dielectric one-dimensional (1D) photonic crystals (PhCs) have been utilized to realize broadband absorption. However, as the incident angle increases, the broadband OTSs in such heterostructures shift towards shorter wavelengths along the PBGs in all-dielectric 1D PhCs, which strongly limits the bandwidths of wide-angle absorption. In this paper, we realize a broadband omnidirectional OTS in a heterostructure composed of a Cr layer and a 1D PhC containing layered hyperbolic metamaterials with an angle-insensitive photonic band gap. Assisted by the broadband omnidirectional OTS, broadband wide-angle absorption can be achieved. High absorptance (A > 0.85) can be remained when the wavelength ranges from 1612 nm to 2335 nm and the incident angle ranges from 0° to 70°. The bandwidth of wide-angle absorption (0°-70°) reaches 723 nm. The designed absorber is a lithography-free 1D structure, which can be easily fabricated under the current magnetron sputtering or electron-beam vacuum deposition technique. This broadband, wide-angle, and lithography-free absorber would possess potential applications in the design of photodetectors, solar thermophotovoltaic devices, gas analyzers, and cloaking devices.

Boosting the photocatalytic hydrogen evolution performance of monolayer C2N coupled with MoSi2N4: density-functional theory calculations.

Very recently, an important two-dimensional material, MoSi2N4, was successfully synthesized. However, pure MoSi2N4 has some inherent shortcomings when used in photocatalytic water splitting to produce hydrogen, especially a low separation rate of photogenerated electron-hole pairs and a poor visible light response. Interestingly, we find that the MoSi2N4 can be used as a good modification material, and it can be coupled with C2N to form an efficient heterojunction photocatalyst. Here, using density functional theory, a type-II heterojunction, C2N/MoSi2N4, is designed and systematically studied. Based on AIMD simulations and phonon dispersion verification, C2N/MoSi2N4 shows sufficient thermodynamic stability. As well as its perfect interface electronic properties, its large interlayer charge transfer and good visible light response lay the foundation for its excellent photocatalytic performance. In addition, the oxidation and reduction potentials of the C2N/MoSi2N4 heterojunction not only can meet the requirements of water splitting well but can also maintain a delicate balance between oxidation and reduction reactions. More importantly, the |ΔGH*| value of the C2N/MoSi2N4 heterojunction is very close to zero, indicating great application potential in the field of photocatalytic water splitting. In brief, our research paves the way for the design of future MoSi2N4-based efficient heterojunction photocatalysts.

Allosteric receptor activation by the plant peptide hormone phytosulfokine.

Phytosulfokine (PSK) is a disulfated pentapeptide that has a ubiquitous role in plant growth and development. PSK is perceived by its receptor PSKR, a leucine-rich repeat receptor kinase (LRR-RK). The mechanisms underlying the recognition of PSK, the activation of PSKR and the identity of the components downstream of the initial binding remain elusive. Here we report the crystal structures of the extracellular LRR domain of PSKR in free, PSK- and co-receptor-bound forms. The structures reveal that PSK interacts mainly with a ß-strand from the island domain of PSKR, forming an anti-ß-sheet. The two sulfate moieties of PSK interact directly with PSKR, sensitizing PSKR recognition of PSK. Supported by biochemical, structural and genetic evidence, PSK binding enhances PSKR heterodimerization with the somatic embryogenesis receptor-like kinases (SERKs). However, PSK is not directly involved in PSKR-SERK interaction but stabilizes PSKR island domain for recruitment of a SERK. Our data reveal the structural basis for PSKR recognition of PSK and allosteric activation of PSKR by PSK, opening up new avenues for the design of PSKR-specific small molecules.

Frequency-tunable terahertz angular selectivity based on a dielectric-graphene multilayer structure.

To achieve frequency-tunable angular selectivity at terahertz frequencies, a tunable epsilon-near-zero (ENZ) metamaterial based on a subwavelength dielectric-graphene multilayer structure is designed. The ENZ frequency of the dielectric-graphene multilayer can be dynamically tuned by the gate voltage applied to graphene. Transmittance angular spectra show that only the incident lights close to normal incidence can propagate through the structure while other incident lights cannot, which indicates that our structure can be utilized for frequency-tunable terahertz angular selection. The optimal directivity D reaches 183 and the transmittance at normal incidence reaches 0.462. This multilayer-based tunable terahertz ENZ metamaterial will possess potential application prospects in tunable highly directive antennas.

Golgi-localized LOT regulates trans-Golgi network biogenesis and pollen tube growth.

The trans-Golgi network (TGN) is an essential tubular-vesicular organelle derived from the Golgi and functions as an independent sorting and trafficking hub within the cell. However, the molecular regulation of TGN biogenesis remains enigmatic. Here we identified an Arabidopsis mutant loss of TGN (lot) that is defective in TGN formation and sterile due to impaired pollen tube growth in the style. The mutation leads to overstacking of the Golgi cisternae and significant reduction in the number of TGNs and vesicles surrounding the Golgi in pollen, which is corroborated by the dispersed cytosolic distribution of TGN-localized proteins. Consistently, deposition of extracellular pectin and plasma membrane localization of kinases and phosphoinositide species are also impaired. Subcellular localization analysis suggests that LOT is localized on the periphery of the Golgi cisternae, but the mutation does not affect the localization of Golgi-resident proteins. Furthermore, the yeast complementation result suggests that LOT could functionally act as a component of the guanine nucleotide exchange factor (GEF) complex of small Rab GTPase Ypt6. Taken together, these findings suggest that LOT is a critical player for TGN biogenesis in the plant lineage.

Calibration-Free Vector Magnetometry Using Nitrogen-Vacancy Center in Diamond Integrated with Optical Vortex Beam.

We report a new method to determine the orientation of individual nitrogen-vacancy (NV) centers in a bulk diamond and use them to realize a calibration-free vector magnetometer with nanoscale resolution. Optical vortex beam is used for optical excitation and scanning the NV center in a [111]-oriented diamond. The scanning fluorescence patterns of NV center with different orientations are completely different. Thus, the orientation information on each NV center in the lattice can be known directly without any calibration process. Further, we use three differently oriented NV centers to form a magnetometer and reconstruct the complete vector information on the magnetic field based on the optically detected magnetic resonance(ODMR) technique. Compared with previous schemes to realize vector magnetometry using an NV center, our method is much more efficient and is easily applied in other NV-based quantum sensing applications.

Both male and female gametogenesis require a fully functional protein S-acyl transferase 21 in Arabidopsis thaliana.

S-Acylation is a reversible post-translational lipid modification in which a long chain fatty acid covalently attaches to specific cysteine(s) of proteins via a thioester bond. It enhances the hydrophobicity of proteins, contributes to their membrane association and plays roles in protein trafficking, stability and signalling. A family of Protein S-Acyl Transferases (PATs) is responsible for this reaction. PATs are multi-pass transmembrane proteins that possess a catalytic Asp-His-His-Cys cysteine-rich domain (DHHC-CRD). In Arabidopsis, there are currently 24 such PATs, five having been characterized, revealing their important roles in growth, development, senescence and stress responses. Here, we report the functional characterization of another PAT, AtPAT21, demonstrating the roles it plays in Arabidopsis sexual reproduction. Loss-of-function mutation by T-DNA insertion in AtPAT21 results in the complete failure of seed production. Detailed studies revealed that the sterility of the mutant is caused by defects in both male and female sporogenesis and gametogenesis. To determine if the sterility observed in atpat21-1 was caused by upstream defects in meiosis, we assessed meiotic progression in pollen mother cells and found massive chromosome fragmentation and the absence of synapsis in the initial stages of meiosis. Interestingly, the fragmentation phenotype was substantially reduced in atpat21-1 spo11-1 double mutants, indicating that AtPAT21 is required for repair, but not for the formation, of SPO11-induced meiotic DNA double-stranded breaks (DSBs) in Arabidopsis. Our data highlight the importance of protein S-acylation in the early meiotic stages that lead to the development of male and female sporophytic reproductive structures and associated gametophytes in Arabidopsis.