Seismic wave amplitudes have tremendous sensitivity to subduction structure; however, they are affected by attenuation, scattering and focusing, and have therefore been sparsely used compared with traveltimes. We measure and model teleseismic body wave amplitudes recorded at a dense broadband array in the Washington Cascades. These data show anomalous amplitude variations with complex azimuthal dependence at frequencies as low as 0.05 Hz, accompanied by significant multipathing. We demonstrate using spectral-element numerical simulations that focusing of the teleseismic wavefield by the Juan de Fuca slab is responsible for some of the amplitude anomalies. The focusing effects can contaminate the apparent differential attenuation measurements and produce at least 20% of the inferred attenuation signal. Our results indicate that the amplitudes are sensitive to the subducting slab geometry and subduction structure, and can be used to refine seismic images. Ubiquitous and consistent amplitude anomalies are observed along the arc, suggesting that the Juan de Fuca slab may be continuous from Canada to northern California.

alpha- and beta-tubulin form heterodimers, with GTPase activity, that assemble into microtubules. Like other GTPases, the nucleotide-bound state of tubulin heterodimers controls whether the molecules are in a biologically active or inactive state. While alpha-tubulin in the heterodimer is constitutively bound to GTP, beta-tubulin can be bound to either GDP (GDP-tubulin) or GTP (GTP-tubulin). GTP-tubulin hydrolyzes its GTP to GDP following assembly into a microtubule and, upon disassembly, must exchange its bound GDP for GTP to participate in subsequent microtubule polymerization. Tubulin dimers have been shown to exhibit rapid intrinsic nucleotide exchange in vitro, leading to a commonly accepted belief that a tubulin guanine nucleotide exchange factor (GEF) may be unnecessary in cells. Here, we use quantitative binding assays to show that BuGZ, a spindle assembly factor, binds tightly to GDP-tubulin, less tightly to GTP-tubulin, and weakly to microtubules. We further show that BuGZ promotes the incorporation of GTP into tubulin using a nucleotide exchange assay. The discovery of a tubulin GEF suggests a mechanism that may aid rapid microtubule assembly dynamics in cells.

In continuation of our comprehensive study of the carbonaceous chondrites, we here present data for the CM chondrites. Our study's aim is to determine the abundances and the average elemental compositions of the major and minor chondritic components. The overarching goal has been to explore the fundamental question of whether chondrules and matrix are complementary, i.e., genetically related, or if these major chondritic components evolved separately before accretion as in the four-component model.

We clarify the nature of hafnia as a proper ferroelectric and show that there is a shallow double well involving a single soft polar mode as in well-known classic ferroelectrics. Using symmetry analysis, density functional theory structural optimizations with and without epitaxial strain, and density functional perturbation theory, we examine several important possible hafnia structures derived ultimately from the cubic fluorite structure, including baddeleyite (P21/c), tetragonal antiferroelectric P42nmc, Pbca (nonpolar and brookite), ferroelectric rhombohedral (R3m and R3), Pmn21, and Pca21 structures. The latter is considered to be the most likely ferroelectric phase seen experimentally and has an antiferroelectric parent with space group Pbcn, with a single unstable polar mode and a shallow double well with a well depth of 24 meV/atom. Strain is not required for switching or other ferroelectric properties, nor is coupling of the soft mode with any other modes within the ferroelectric Pca21, Pmn21, R3m, or R3 phases.

The development of multi-cellular organisms requires coordinated changes in gene expression that are often mediated by the interaction between transcription factors (TFs) and their corresponding cis-regulatory elements (CREs). During development and differentiation, the accessibility of CREs is dynamically modulated by the epigenome. How the epigenome, CREs and TFs together exert control over cell fate commitment remains to be fully understood. In the Arabidopsis leaf epidermis, meristemoids undergo a series of stereotyped cell divisions, then switch fate to commit to stomatal differentiation. Newly created or reanalyzed scRNA-seq and ChIP-seq data confirm that stomatal development involves distinctive phases of transcriptional regulation and that differentially regulated genes are bound by the stomatal basic-helix-loop-helix (bHLH) TFs. Targets of the bHLHs often reside in repressive chromatin before activation. MNase-seq evidence further suggests that the repressive state can be overcome and remodeled upon activation by specific stomatal bHLHs. We propose that chromatin remodeling is mediated through the recruitment of a set of physical interactors that we identified through proximity labeling - the ATPase-dependent chromatin remodeling SWI/SNF complex and the histone acetyltransferase HAC1. The bHLHs and chromatin remodelers localize to overlapping genomic regions in a hierarchical order. Furthermore, plants with stage-specific knock-down of the SWI/SNF components or HAC1 fail to activate specific bHLH targets and display stomatal development defects. Together these data converge on a model for how stomatal TFs and epigenetic machinery cooperatively regulate transcription and chromatin remodeling during progressive fate specification.

Protein-protein interactions play a crucial role in driving cellular processes and enabling appropriate physiological responses in organisms. The plant hormone ethylene signaling pathway is complex and regulated by the spatiotemporal regulation of its signaling molecules. Constitutive Triple Response 1 (CTR1), a key negative regulator of the pathway, regulates the function of Ethylene-Insensitive 2 (EIN2), a positive regulator of ethylene signaling, at the endoplasmic reticulum (ER) through phosphorylation. Our recent study revealed that CTR1 can also translocate from the ER to the nucleus in response to ethylene and positively regulate ethylene responses by stabilizing EIN3. To gain further insights into the role of CTR1 in plants, we used TurboID-based proximity labeling and mass spectrometry to identify the proximal proteomes of CTR1 in Nicotiana benthamiana. The identified proximal proteins include known ethylene signaling components, as well as proteins involved in diverse cellular processes such as mitochondrial respiration, mRNA metabolism, and organelle biogenesis. Our study demonstrates the feasibility of proximity labeling using the N. benthamiana transient expression system and identifies the potential interactors of CTR1 in vivo, uncovering the potential roles of CTR1 in a wide range of cellular processes.

Recent discoveries of gas giant exoplanets around M-dwarfs from transiting and radial velocity surveys are difficult to explain with core-accretion models. We present here a homogeneous suite of 162 models of gravitationally unstable gaseous disks. These models represent an existence proof for gas giants more massive than 0.1 Jupiter masses to form by the gas disk gravitational instability (GDGI) mechanism around M-dwarfs for comparison with observed exoplanet demographics and protoplanetary disk mass estimates for M-dwarf stars. We use the Enzo 2.6 adaptive mesh refinement (AMR) 3D hydrodynamics code to follow the formation and initial orbital evolution of gas giant protoplanets in gravitationally unstable gaseous disks in orbit around M-dwarfs with stellar masses ranging from 0.1 M circle dot to 0.5 M circle dot. The gas disk masses are varied over a range from disks that are too low in mass to form gas giants rapidly to those where numerous gas giants are formed, therefore revealing the critical disk mass necessary for gas giants to form by the GDGI mechanism around M-dwarfs. The disk masses vary from 0.01 M circle dot to 0.05 M circle dot while the disk to star mass ratios explored the range from 0.04 to 0.3. The models have varied initial outer disk temperatures (10-60 K) and varied levels of AMR grid spatial resolution, producing a sample of expected gas giant protoplanets for each star mass. Broadly speaking, disk masses of at least 0.02 M circle dot are needed for the GDGI mechanism to form gas giant protoplanets around M-dwarfs.

Mantle xenoliths in a Mesoproterozoic lamprophyre dyke at Elliot Lake, Ontario, located on the east margin of the Midcontinent Rift (MCR), erupted at similar to 1.1 Ga. These xenoliths enable a study of critical metal enrichment in the sub-cratonic lithospheric mantle (SCLM). Whole-rock major and trace element data from a suite of peridotite xenoliths document a combination of melt depletion and cryptic metasomatic processes. Trace element whole-rock and mineral systematics show a specific endowment in Nb-U-REE (ca. 5-30 ppm mean value), linked to carbonated silicate metasomatism. Geochronological data from the lamprophyre host (Rb-Sr age of 1112.8 +/- 4.95 Ma) and the mantle xenoliths (Re-Os) indicate that our samples document the state of the mantle during the earlier stages of magmatism of the MCR. Mineral thermobarometry reveals a hot geotherm reflecting the thinning of the Superior cratonic root to 110 km. Most of the Nb-U-REE deposits and anomalies associated with the MCR event are located around Lake Superior. Here we document for the first time north of Lake Huron, metasomatic processes in the lithosphere that may have created Nb-U-REE metal endowment. The mantle events documented here relate to other observations made in the Slave and North China craton and show how silico-carbonated mid-lithospheric metasomatism up-grades the cratonic lithospheric mantle into a fertile source. Comparison with other small degree melts such as kimberlites, and mantle metasomes related to the MARID suite, show that small degree melts are very efficient at transporting critical metals from the HFSE group plus U and Th, into Earth's lithosphere.

The mineral kingdom has experienced dramatic increases in diversity and complexity through billions of years of planetary evolution as a consequence of a sequence of physical, chemical, and biological processes. Each new formational environment, or "mineral paragenetic mode," has its own characteristic attributes, including the stage of mineral evolution and geological age, ranges of T, P, duration of formation events, and other environmental influences on mineral formation. Furthermore, the minerals associated with each paragenetic mode have a wide range of average properties, including hardness, density, and chemical and structural complexity. A survey of attributes of 57 mineral paragenetic modes representing the full range of mineral-forming processes reveals systematic trends, including: (1) minerals documented from older paragenetic processes are systematically harder on average than those from more recent processes; (2) minerals from paragenetic modes formed at lower T (notably <500 K) display greater average structural complexity than those formed at high T (especially >1000 K); and (3) minerals from paragenetic modes that display greater average chemical complexity are systematically less dense than those from modes with lesser average chemical complexity. In addition, minerals formed in anhydrous environments and/or by abiotic processes are, on average, significantly denser and harder than those formed in hydrous environments and/or by biotic processes.