The maize female gametophyte is comprised of four cell types: two synergids, an egg cell, a central cell, and a variable number of antipodal cells. In maize, these cells are produced after three rounds of free-nuclear divisions followed by cellularization, differentiation, and proliferation of the antipodal cells. Cellularization of the eight-nucleate syncytium produces seven cells with two polar nuclei in the central cell. Nuclear localization is tightly controlled in the embryo sac. This leads to precise allocation of the nuclei into the cells upon cellularization. Nuclear positioning within the syncytium is highly correlated with their identity after cellularization. Two mutants are described with extra polar nuclei, abnormal antipodal cell morphology, and reduced antipodal cell number, as well as frequent loss of antipodal cell marker expression. Mutations in one of these genes, indeterminate gametophyte2 encoding a MICROTUBULE ASSOCIATED PROTEIN65-3 homolog, shows a requirement for MAP65-3 in cellularization of the syncytial embryo sac as well as for normal seed development. The timing of the effects of ig2 suggests that the identity of the nuclei in the syncytial female gametophyte can be changed very late before cellularization.

Astrophysics and cosmology in the coming decades urgently need a large field-of-view (FOV), highly multiplexed spectroscopic survey telescope satisfying challenging image quality and stability requirements. The 6.5 m MUltiplexed Survey Telescope (MUST) proposed by Tsinghua University will be constructed on the Saishiteng Mountain of Northwest China to improve the spectroscopic survey capability of ground-based optical telescopes. In this paper, we demonstrate the conceptual design of the optical system of MUST. MUST will adopt a 6.5 m primary mirror, a 2.45 m secondary mirror, and a multiple-element widefield corrector (WFC) to ensure excellent image quality with an 80% encircled energy size of image spots less than similar to 0.6 arcsec in diameter for the entire 3 degrees FOV and the whole 50 degrees zenith angle range. Thanks to its compact 6.5 m Ritchey-Chretien system and 20,000 optical fibers on its Cassegrain focus, MUST will carry out state-of-the-art wide-field spectroscopic surveys with efficiency similar to 19 times higher than the Dark Energy Spectroscopic Instrument (DESI) using a measure proposed by Ellis et al. Upon completion around 2029, MUST will be one of the world's most advanced wide-field spectroscopic survey telescopes and a new essential reference for the future development of wide-field survey telescopes. It will enable significant advances in many fields in astrophysics and cosmology.

JWST observations of polycyclic aromatic hydrocarbon (PAH) emission provide some of the deepest and highest resolution views of the cold interstellar medium (ISM) in nearby galaxies. If PAHs are well mixed with the atomic and molecular gas and illuminated by the average diffuse interstellar radiation field, PAH emission may provide an approximately linear, high-resolution, high-sensitivity tracer of diffuse gas surface density. We present a pilot study that explores using PAH emission in this way based on Mid-Infrared Instrument observations of IC 5332, NGC 628, NGC 1365, and NGC 7496 from the Physics at High Angular resolution in Nearby GalaxieS-JWST Treasury. Using scaling relationships calibrated in Leroy et al., scaled F1130W provides 10-40 pc resolution and 3 sigma sensitivity of sigma(gas) similar to 2 M (circle dot) pc(-2). We characterize the surface densities of structures seen at M (circle dot) pc(-2) in our targets, where we expect the gas to be H i-dominated. We highlight the existence of filaments, interarm emission, and holes in the diffuse ISM at these low surface densities. Below similar to 10 M (circle dot) pc(-2) for NGC 628, NGC 1365, and NGC 7496 the gas distribution shows a "Swiss cheese"-like topology due to holes and bubbles pervading the relatively smooth distribution of the diffuse ISM. Comparing to recent galaxy simulations, we observe similar topology for the low-surface-density gas, though with notable variations between simulations with different setups and resolution. Such a comparison of high-resolution, low-surface-density gas with simulations is not possible with existing atomic and molecular gas maps, highlighting the unique power of JWST maps of PAH emission.

Corals form an endosymbiotic relationship with the dinoflagellate algae Symbiodiniaceae, but ocean warming can trigger algal loss, coral bleaching and death, and the degradation of ecosystems. Mitigation of coral death requires a mechanistic understanding of coral-algal endosymbiosis. Here we report an RNA interference (RNAi) method and its application to study genes involved in early steps of endosymbiosis in the soft coral Xenia sp. We show that a host endosymbiotic cell marker called LePin (lectin and kazal protease inhibitor domains) is a secreted Xenia lectin that binds to algae to initiate phagocytosis of the algae and coral immune response modulation. The evolutionary conservation of domains in LePin among marine anthozoans performing endosymbiosis suggests a general role in coral-algal recognition. Our work sheds light on the phagocytic machinery and posits a mechanism for symbiosome formation, helping in efforts to understand and preserve coral-algal relationships in the face of climate change.

The intestines of animals are colonized by commensal microbes, which impact host development, health, and behavior. Precise quantification of colonization is essential for studying the complex interactions between host and microbe both to validate the microbial composition and study its effects. Drosophila melanogaster, which has a low native microbial diversity and is economical to rear with defined microbial composition, has emerged as a model organism for studying the gut microbiome. Analyzing the microbiome of an individual organism requires identification of which microbial species are present and quantification of their absolute abundance. This article presents a method for the analysis of a large number of individual fly microbiomes. The flies are prepared in 96-well plates, enabling the handling of a large number of samples at once. Microbial abundance is quantified by plating up to 96 whole fly homogenates on a single agar plate in an array of spots and then counting the colony forming units (CFUs) that grow in each spot. This plating system is paired with an automated CFU quantification platform, which incorporates photography of the plates, differentiation of fluorescent colonies, and automated counting of the colonies using an ImageJ plugin. Advantages are that (i) this method is sensitive enough to detect differences between treatments, (ii) the spot plating method is as accurate as traditional plating methods, and (iii) the automated counting process is accurate and faster than manual counting. The workflow presented here enables high-throughput quantification of CFUs in a large number of replicates and can be applied to other microbiology study systems including in vitro and other small animal models.

We model the early stages of planet formation in the solar system, including continual planetesimal formation, and planetesimal and pebble accretion onto planetary embryos in an evolving disk driven by a disk wind. The aim is to constrain aspects of planet formation that have large uncertainties by matching key characteristics of the solar system. The model produces a good fit to these characteristics for a narrow range of parameter space. Planetary growth beyond the ice line is dominated by pebble accretion. Planetesimal accretion is more important inside the ice line. Pebble accretion inside the ice line is slowed by higher temperatures, partial removal of inflowing pebbles by planetesimal formation and pebble accretion further out in the disk, and increased radial velocities due to gas advection. The terrestrial planets are prevented from accreting much water ice because embryos beyond the ice line reach the pebble-isolation mass before the ice line enters the terrestrial-planet region. When only pebble accretion is considered, embryos typically remain near their initial mass or grow to the pebble-isolation mass. Adding planetesimal accretion allows Mars-sized objects to form inside the ice line, and allows giant-planet cores to form over a wider region beyond the ice line. In the region occupied by Mercury, pebble Stokes numbers are small. This delays the formation of embryos and stunts their growth, so that only low-mass planets can form here.

BackgroundGenetic variation in regulatory sequences that alter transcription factor (TF) binding is a major cause of phenotypic diversity. Brassinosteroid is a growth hormone that has major effects on plant phenotypes. Genetic variation in brassinosteroid-responsive cis-elements likely contributes to trait variation. Pinpointing such regulatory variations and quantitative genomic analysis of the variation in TF-target binding, however, remains challenging. How variation in transcriptional targets of signaling pathways such as the brassinosteroid pathway contributes to phenotypic variation is an important question to be investigated with innovative approaches.ResultsHere, we use a hybrid allele-specific chromatin binding sequencing (HASCh-seq) approach and identify variations in target binding of the brassinosteroid-responsive TF ZmBZR1 in maize. HASCh-seq in the B73xMo17 F1s identifies thousands of target genes of ZmBZR1. Allele-specific ZmBZR1 binding (ASB) has been observed for 18.3% of target genes and is enriched in promoter and enhancer regions. About a quarter of the ASB sites correlate with sequence variation in BZR1-binding motifs and another quarter correlate with haplotype-specific DNA methylation, suggesting that both genetic and epigenetic variations contribute to the high level of variation in ZmBZR1 occupancy. Comparison with GWAS data shows linkage of hundreds of ASB loci to important yield and disease-related traits.ConclusionOur study provides a robust method for analyzing genome-wide variations of TF occupancy and identifies genetic and epigenetic variations of the brassinosteroid response transcription network in maize.

We report new total-intensity visible-light high-contrast imaging of the TW Hya disk taken with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope. This represents the first published images of the disk with STIS since 2016, when a moving shadow on the disk surface was reported. We continue to see the shadow moving in a counterclockwise fashion, but in these new images the shadow has evolved into two separate shadows, implying a change in behavior for the occulting structure. Based on radiative-transfer models of optically thick disk structures casting shadows, we infer that a plausible explanation for the change is that there are now two misaligned components of the inner disk. The first of these disks is located between 5 and 6 au with an inclination of 5.5 degrees and position angle (PA) of 170 degrees, and the second between 6 and 7 au with an inclination of 7 degrees and PA of 50 degrees. Finally, we speculate on the implications of the new shadow structure and determine that additional observations are needed to disentangle the nature of TW Hya's inner-disk architecture.

We use observations with the infrared-optimized Magellan Adaptive Optics (MagAO) system and Clio camera in 3.9 mu m light to place stringent mass constraints on possible undetected companions to Sirius A. We suppress the light from Sirius A by imaging it through a grating vector-apodizing phase plate coronagraph with a 180 degrees dark region (gvAPP-180). To remove residual starlight in postprocessing, we apply a time-domain principal-components-analysis-based algorithm we call PCA-Temporal, which uses eigen time series rather than eigenimages to subtract starlight. By casting the problem in terms of eigen time series, we reduce the computational cost of postprocessing the data, enabling the use of the fully sampled data set for improved contrast at small separations. We also discuss the impact of retaining fine temporal sampling of the data on final contrast limits. We achieve postprocessed contrast limits of 1.5 x 10(-6)-9.8 x 10(-6) outside of 0.'' 75, which correspond to planet masses of 2.6-8.0 M (J). These are combined with values from the recent literature of high-contrast imaging observations of Sirius to synthesize an overall completeness fraction as a function of mass and separation. After synthesizing these recent studies and our results, the final completeness analysis rules out 99% of >= 9 M (J) planets from 2.5 to 7 au.