Fold System Research Articles

Shortening a mixed salt and mobile shale system: A case study from East Breaks, northwest Gulf of Mexico

The coexistence of two low-shear strength layers in a continental margin, such as salt and shales, conditions the resulting structural style and also constitutes a challenge for seismic imaging and energy resource exploration. We have analyzed the 3D structure of a mixed salt-shale system in the western Gulf of Mexico, in the East Breaks foldbelt, by interpreting a depth-migrated seismic data set. Overlying the allochthonous Sigsbee canopy and pierced by isolated salt diapirs, the Oligocene shale-prone sequences were shortened during the Miocene through pervasive deformations, developing a major suprasalt detachment system associated with duplexes below and different fold and thrust systems above. Oligocene shales locally reach a critical state and flow, resulting in: (1) inflated shale-cored detachment anticlines, with the stacking of allochthonous mobile shale domains; (2) detached lift-off anticlines with shale bulbs and fishtail thrusted welds; (3) allochthonous shale sheets at the upper tip of thrusts, fed by fluidized material migrating along associated fault zones; (4) hourglass shale diapirs; and (5) Christmas trees and vertical mud pipes connected to small mud volcanoes. The salt diapirs deformed simultaneously, as did the shales. Salt accommodated the shortening through localized subvertical welds that isolated them from the allochthonous Sigsbee canopy and through weld thrusts formed by fault-bounded blocks with highly sheared salt and mobile shales. Mobile shale structures wrap around the squeezed salt diapirs, presenting a unique pattern that has not yet been documented in experimental models with precursor salt diapirs deformed under contraction. Mixed salt-shale systems are a new challenge for structural analysis and experimental models, as well as for seismic model building in situations where there is a high dispersion of seismic energy due to the unique properties of mobile shales.

Pernambuco-Alagoas, Riacho do Pontal, and Sergipano domains of the Borborema Province, Northeastern Brazil: a geological and geochronological synthesis

Abstract In recent years, the number of works seeking to advance the geological and geotectonic knowledge of the Borborema Province has been increasing. However, in the context of the Southern Borborema Province there are few studies aimed at understanding its tectonic evolution in an integrated way. This work presents a review of the lithostratigraphic and geochronological data available for the Pernambuco-Alagoas, Riacho do Pontal and Faixa Sergipana Domains, located in the southern portion of the Borborema Province (Northeast Brazil), in addition to a discussion on the tectonic evolution model. The Southern Borborema Province fully encompasses the state of Alagoas and partially the states of Pernambuco, Sergipe, Bahia and Piauí, and is delimited to the north by the Pernambuco Lineament and to the south by the São Francisco Craton. The methodology involved bibliographical survey, geological cartography, geochronological compilation, creation of detrital zircon histograms for metasedimentary rocks (with unconformity below 10%) and magmatic “barcodes” for ortho-derived rocks and preparation of regional geological profiles. The tectonic evolution of the Southern Borborema Province began with the breakup of the Rodínia Supercontinent (1000 Ma) during the Cariris Velhos Cycle. The processes involved in the interaction of fragments descending from Rodinia are diachronic, in a broad scenario of accretions and collisions that resulted in the merger of Gondwana. The Pernambuco-Alagoas Block is considered a complex tectonic domain, which was affected by the Cariris Velhos (1000 – 950 Ma) and Brasiliana (740 - 570 Ma) orogenies (Caxito & Alkmim 2023), preserving remnants of Archean rocks (Riacho Seco Fragment) and proterozoic. The Riacho do Pontal Domain and the Faixa Sergipana Domain are part of a large folding system formed from the collision of the Pernambuco-Alagoas Domain with the São Francisco Craton, in a tangential deformation, vergent towards the craton, during the Brasiliana Orogeny. From the ages of the syncollisional granites we can infer that the orogenic event that gave rise to the aforementioned folded bands occurred at very close time intervals, presenting a slight diachronism. The article presents an integrated approach to tectonic evolution, however, the need for new studies is quite evident, with an emphasis on isotopic geology, geochronology, geochemistry and geological mapping that can contribute to the understanding of the processes involved in the formation of tectonic domains, their space-time relationships and their implications for the evolution of the Gondwana Continent.

Features of the continental volcanic-plutonic belts of the Junggar-Balkhash fold system

Purpose. The study aims to investigate the formation composition and structural-formation zoning of the Late Paleozoic continental volcanic and volcano-sedimentary formations of the Junggar-Balkhash fold system (JBFS). It also seeks to define the geological-geophysical characteristics and metallogenic specialization of the volcanic-plutonic belts (VPB) in the region. Methods. The research utilizes data from detailed mapping and analysis of Late Paleozoic magmatites in JBFS over the past 10-40 years. Structural-formation zoning of the region was performed from an actualistic perspective, along with the formation typification of stratified and intrusive ore formations. The study of metallogenic specialization was conducted considering modern geophysical research methods. Findings. Two main volcanic-plutonic belts have been identified: the Carboniferous marginal-continental Tasty-Kusak-Kotyryasan-Altunemel Belt and the Carboniferous-Permian intracontinental Balkhash-Ili Belt, which together cover about 80% of the JBFS territory. The geological-geophysical characteristics and metallogenic specialization of these belts have been defined. In particular, the findings highlight significant prospects for epithermal gold-silver and copper-porphyry mineralization. Originality. For the first time, a structural-formation zoning of JBFS has been conducted, and the typification of volcanic-Plutonic Belts has been substantiated. Additionally, their metallogenic specialization has been determined, revealing patterns of localization for epithermal gold-silver and copper-porphyry deposits. Practical implications. The study’s results are of great importance for exploration geology, contributing to the improved efficiency of searching for ore deposits in the region, particularly epithermal gold-silver and copper-porphyry targets.

Santos Basin as an Example of a Shear-Driven Core Complex in a Transform Marginal Plateau

It is proposed a new model on the kinematics of strain partitioning for the breakup of the Santos and Namibe conjugate basins. The model is based on observed strike-slip corridors and low-angle detachments with metamorphic core complexes, which accommodated the deformation in a mega relay zone. Through detailed reconstructions of this segment of the South Atlantic, collecting multidisciplinary data from previous researchers, and considering the relative relationship between Africa and South America during the breakup process, it is herein reexamined key evidence of how the Brazilian side became so wide, and acted as an accommodation zone during the Aptian. The 600 km Long transpressional-dextral Proterozoic Ribeira Belt is the cradle of the transtensional-sinistral Santos-Namibe strike-slip rift propagator. These conjugate basins evolved as a large-scale relay zone, developing an oblique-left-lateral extensional corridor during the Aptian, balancing mechanically coeval deformations from two sub-parallel spreading branches, traveling from North and South, but hundreds of kilometers apart from each other. Proterozoic inheritance, and the dynamic clockwise rotation of South America (far-field stresses) controlled strain partitioning between the Campos/Benguela basins and the Pelotas/Walvis basins. The onset of seafloor spreading around the Falkland (Malvinas) Island, triggered the relative clockwise rotation of the southernmost tip of the South America plate, and the intrusion of transversal dike swarms of the Ponta Grossa Arch, which is interpreted as fissural magmatism, comparable to a regional opening mode(type I) fracture system. Plate kinematic transport direction inferred from plate reconstructions is mainly EW. The step-over oblique-slip of this relay zone widened the Santos Basin in the NW-SE direction, often mistakenly misinterpreted as the extension direction in the Santos Basin. This NW path is the direction of the maximum elongation within an E-W shear corridor. Our work details a new and unprecedented strike-slip structural framework of the Santos Basin, with large-scale basement-involved folding around the Outer High, which evolved to an obliquely sheared active low-angle detachment system, simultaneously influenced by the thermal anomaly of the Tristan-Gough plume, responsible for magmatic thermal weakening and thermal-induced uplift. Magmatic underplating may have facilitated the doming process. The Santos Basin is located at the heart of a Transform Marginal Plateau, as previously proposed. It is composed of a magmatic crust, with fragmented slices of continental crust, obliquely sheared during successive transform movements, with possible magmatic underplating. This kinematically linked system of normal faults, strike-slip faults, flexural folds, and detachment faults has direct impact on understanding the properties of world-class oil and gas reservoirs in the Brazilian Pre-Salt Supergiant Province. With the ongoing regional transgression, the active structural highs were the site of deposition of the carbonate reservoirs that host an in-place volume around a hundred billion barrels of hydrocarbons, considering the whole province.

Mantle-plume model for the Zun-Kholba orogenic gold deposit (Eastern Sayan, Russia): results of mineralogical, Rb-Sr and <sup>40</sup>Ar-<sup>39</sup>Ar geochronological and Pb-Pb isotopic studies

The large Zun-Kholba deposit, belonging to a numerous group of orogenic-type gold deposits, is in the Eastern Sayan (Russia) – a segment of the Altai-Sayan fold system of the Central Asian Orogenic Belt. The paper discusses the results of mineralogical, geochemical, geochronological and Pb-isotopic studies of gold mineralization, the purpose of which was to verify the genetic model of the deposit. Mineralogical and geochemical data obtained for ore bodies located between hypsometric levels from 1290 to 2090 m indicate a complex distribution of mineral associations at the deposit. There is no vertical and horizontal zonation in the distribution of mineral associations, in the chemical composition of the main ore minerals, as well as in the content of impurity elements in them. In dating ore-forming processes at the Zun-Kholba deposit, a comprehensive approach based on the study of K-Ar and Rb-Sr isotope systems of metasomatites was applied. The combination of Rb-Sr and 40Ar-39Ar methods allowed us to determine that the age of gold mineralization is 411 ± 2 Ma, while the age of the superimposed event, which is associated with redistribution of ore, as well as disturbance of the Rb-Sr and K-Ar isotopic systems of metasomatites, is about 380 Ma. Pb-Pb isotopic study of ore mineralization at the deposit and host Precambrian rocks allowed to prove the leading contribution of the latter in ore lead supply to the mineral-forming system. The model of formation of the Zun-Kholba orogenic gold deposit assumes a genetic relationship between ore-forming processes and intraplate alkaline mafic magmatism due to the impact of the plume in the Early Devonian time on the lithosphere of the Tuva-Mongolian terrane.

Seismo-stratigraphic and morpho-bathymetric analysis revealing recent fluid-rising phenomena on the Adventure Plateau (northwestern Sicily Channel)

The northwestern region of the Sicily Channel hosts a great number of morphological highs, the widest of which is the Adventure Plateau that is part of the Sicilian Maghrebian Fold and Thrust Belt system, formed since the Neogene. The Adventure Plateau was shaped in the Early Pliocene by an extensional phase that produced high-angle normal faults mostly WNW-ESE to N-S oriented. Through these faults, magmatic fluids ascended and produced widespread volcanic manifestations often associated to fluid flow processes. The interpretation of multibeam echosounder, seismic reflection (sparker, airgun) and well-log data allow us to identify several features related to the presence of fluids in the study area. The morpho-structural analysis showed a NW–SE oriented fault system and a string of pockmarks that follow the same trend. A detailed well-log analysis confirmed the presence of oil traces, at a depth of ~ 250 m, and gas (i.e., CO2) at a depth of ~ 450 m. The seismo-stratigraphic analysis highlighted seismic signals located below the pockmarks, (e.g. seismic chimneys, bright spots) which suggest the presence of fluids that would rise to a few meters’ depth. Based on the observations, two sources and two corresponding rising mechanisms have been identified. Morphometric analysis of pockmarks has been performed to delineate their possible interaction with the bottom currents. A fluids pathway model has been reconstructed, revealing the source of fluids emissions at depth in the Adventure Plateau, and providing new insights into the identification of fluid leakage pathways.

On the Crustal Sources of Magnetic Anomalies in the Middle Urals

The 800×500 sq km area of the the Middle Urals, Russia, lying between 56 to 60° northern latitude and 54 to 66° eastern longitude, was studied in terms of the deep crustal structure. The study was based on three-dimensional modeling of the sources of magnetic anomalies in three layers of the Earth’s crust. The studied area covers the folded region of the Urals and adjacent structures of the East European Platform and the West Siberian Plate. The sources modeled in the near-surface layer down to a depth of 5 km make it possible to clarify the position of magnetized massifs, mainly consisting of mafic-ultrabasic rocks, and to trace their connection with mafic-ultrabasic belts in the granite layer and root blocks in the lower basaltic layer of the Earth’s crust. When the sources in the upper crustal layer are compared with those in the lower crustal layer, it is apparent that many belts on the platform have deep-seated roots and are located above the basalt layer protrusions, while most of the massifs in the Urals do not have deep-seated roots. The springs located under the western slope of the Urals allow reliably determining the depth to the basement of the ancient platform and the location of the eastern border of the East European Platform in the lower layer of the Earth’s crust. There were found extended zones of subsidence of the roof of the lower magnetized layer, which probably mark the boundaries of various terrains forming the paleo-island arc sector of the Ural fold system. The most extensive subsidence of the roof of the lower layer occurs to the west of the Tyumen-Chudinovsky fault and is perhaps the eastern deep-seated dividing line between the Ural fold system and the West Siberian Plate.

Глубинное строение Среднего Урала по гравитационным и магнитным данным

For the Middle Urals and adjacent territories of the East European and West Siberian platforms within geographic coordinates from 56º to 60º northern latitude and from 54º to 66º east longitude, the structural features of the anomalous magnetic and gravitational fields were studied and maps of separated anomalies were constructed for three layers of the earth's crust. Using original parallel algorithms for solving forward and inverse problems of gravimetry and magnetometry, a density model of the lithosphere and sources of magnetic anomalies in the earth's crust were constructed. The results of modeling the sources of magnetic anomalies in the Earth's crust are compared with the density model in order to study the differences in the deep structure of the western paleocontinental and eastern paleo-island arc sectors of the Ural fold system, as well as the zones of junction of the orogen with the East European and West Siberian platforms.

Growth of the northeastern Tibetan plateau since the Middle Miocene as revealed by syn-tectonic growth strata

Syn-tectonic deposition of sediments (growth strata) preserves a direct record of mountain building-erosion and basin deformation. When and how these sediments incorporated into forward propagating fold-and-thrust (FTB) belts can shed light on the above processes. Despite many years of research, there is still ongoing debate about the timing and mechanisms of the southern Qaidam fold-and-thrust belt in the northeastern Tibetan Plateau. Here, we provide insight into the deformation of the Qaidam Basin and the broader tectonic processes of the northeastern Tibetan Plateau through detailed analysis of the Dafengshan (DFS), Jiandingshan (JDS) and Heiliangzi (HLZ) anticlines along the southern Qaidam FTB. Identification of the growth strata by Area-Depth analysis and age determination indicate that deformation of the DFS anticline initiated in the mid-Miocene (∼15 Ma), and has successively experienced lateral growth (∼15–8.0 Ma) and uplift (∼8.0 Ma-present). This timeline of deformation coincides with periods of mountain building in the northeastern Tibetan Plateau and might be related to the removal of mantle beneath northern Tibet. The synchronization of growth strata with an increase in sedimentation and exhumation rates reveals the reactivation of the tectonic belt around the basin in the mid-Miocene, creating the current basin-range landform; since ∼8 Ma, compression has expanded rapidly into the interior of the Qaidam Basin, leading to incorporation of basin deposits into the FTB. Geomorphological analyses coupled with 3-D fold modeling demonstrate that the JDS and HLZ-fold train with S-shaped configuration is a coherent fold system developed by lateral growth and linkage of two different fold segments in the context of the N–S directional compression of the plateau. Considering the prevalent S-shaped constructions within the basin and the current seismicity, we propose that the dominant structures in the southwestern Qaidam Basin are a series of thrust faults and folds controlled by the compression component of the East Kunlun Fault, with a limited influence from the Altyn Tagh Fault.

ATM-mediated co-chaperone DNAJB11 phosphorylation facilitates α-synuclein folding upon DNA double-stranded breaks

Abstract Parkinson's disease (PD) is a prevalent neurodegenerative disorder marked by the pathological accumulation of α-synuclein aggregates in dopaminergic neurons. This α-synuclein dyshomeostasis is caused by an interplay between aging, genetic and environmental factors. Aging process-related DNA damage and impaired DNA repair have recently been observed in the PD process. However, the precise neuronal response to DNA damage in PD remains largely unknown. Here, we demonstrate that double-strand breaks (DSBs) induce α-synuclein aggregation. Analysis of a large-scale proteomic analysis of ATM and ATR substrates identified a potential candidate in the HSP70 folding system responding to DNA damage. ATM phosphorylates co-chaperone DNAJB11 at threonine 188 which specifically facilitates the delivery of misfolded α-synuclein, but not tau or transthyretin protein, to the HSP70 folding system upon DSBs. Alteration of this response impairs the neurite outgrowth. Remarkably, DNAJB11 threonine 188 phosphorylation correlates with disease severity in transgenic SNCA mutant PD mice and PD patients. These findings reveal a DNA damage-responded HSP70 folding mechanism through a J-domain co-chaperone, offering a potential therapeutic target for PD.

Proteostatic tuning underpins the evolution of novel multicellular traits.

The evolution of multicellularity paved the way for the origin of complex life on Earth, but little is known about the mechanistic basis of early multicellular evolution. Here, we examine the molecular basis of multicellular adaptation in the multicellularity long-term evolution experiment (MuLTEE). We demonstrate that cellular elongation, a key adaptation underpinning increased biophysical toughness and organismal size, is convergently driven by down-regulation of the chaperone Hsp90. Mechanistically, Hsp90-mediated morphogenesis operates by destabilizing the cyclin-dependent kinase Cdc28, resulting in delayed mitosis and prolonged polarized growth. Reinstatement of Hsp90 or Cdc28 expression resulted in shortened cells that formed smaller groups with reduced multicellular fitness. Together, our results show how ancient protein folding systems can be tuned to drive rapid evolution at a new level of biological individuality by revealing novel developmental phenotypes.

Nonlinear dynamics and chaos in a vocal-ventricular fold system.

In humans, ventricular folds are located superiorly to the vocal folds. Under special circumstances such as voice pathology or singing, they vibrate together with the vocal folds to contribute to the production of voice. In the present study, experimental data measured from physical models of the vocal and ventricular folds were analyzed in the light of nonlinear dynamics. The physical models provide a useful experimental framework to study the biomechanics of human vocalizations. Of particular interest in this experiment are co-oscillations of the vocal and ventricular folds, occasionally accompanied by irregular dynamics. We show that such a system can be regarded as two coupled oscillators, which give rise to various cooperative behaviors such as synchronized oscillations with a 1:1 or 1:2 frequency ratio and desynchronized oscillations with torus or chaos. The insight gained from the view of nonlinear dynamics should be of significant use for the diagnosis of voice pathologies, such as ventricular fold dysphonia.

Gravity flow deposits in Mesozoic sediments of Chukotka microplate (North‐East Russia)

AbstractIn the Mesozoic succession of the Anyui–Chukotka fold system (North‐East Russia), five stratigraphic intervals were recognised that have an abundance of gravity flow deposits. These are the Olenekian (Lower Triassic), Upper Carnian, Upper Norian, Oxfordian–Kimmeridgian and Valanginian. The Triassic gravity flow deposits formed on the south‐facing, passive margin of the Chukotka microplate and consist of greywackes and lithic arenites. Palaeocurrent data indicate that the flows were directed towards the south‐east. The Olenekian gravity flow units consist of clast‐rich sandstone deposited on the continental slope, and clast‐poor sandstone deposited at the base of the slope. Upper Carnian mud‐poor sandstones were deposited at the base of the slope and the Norian thin‐bedded turbidites were upper to mid‐slope deposits. The continental margin was affected by tectonism and was uplifted in the latest Triassic–earliest Jurassic, possibly due to the initiation of the southward translation of the Arctic Alaska–Chukotka microplate. Following an Early–Middle Jurassic uplift of the area, sedimentation resumed in the Late Jurassic and earliest Cretaceous. Several syn‐orogenic depressions (Rauchua, Pegtymel, Pevek, Myrgovaam and Kytepveem) developed on the south‐western margin of the Chukotka microplate, and deposition in these basins included gravity flow deposits at various times. In both the Oxfordian–Kimmeridgian and Valanginian successions, gravity flow deposits included arkosic and subarkosic sandstones with a northern source area of granitoid complexes and deformed Triassic strata. The intervening Tithonian–Berriasian gravity flow deposits consisted mainly of thin‐bedded turbidites. These sediments had a southern source, which included a volcanic arc that had accreted to the southern margin of the Chukotka microplate.

Omics-Based Investigation on Mechanisms Controlling Cellular Internalization of Keratin Monomers during Biodegradation by Stenotrophomonas maltophilia DHHJ.

The global poultry industry produces millions of tons of waste feathers every year, which can be bio-degraded to make feed, fertilizer, and daily chemicals. However, feather bio-degradation is a complex process that is not yet fully understood. This results in low degradation efficiency and difficulty in industrial applications. Omics-driven system biology research offers an effective solution to quickly and comprehensively understand the molecularmechanisms involved in a metabolic pathway. In the early stage of this process, feathers are hydrolyzed into water-soluble keratin monomers. In this study, we used high-throughput RNA-seq technology to analyze the genes involved in the internalization and degradation of keratin monomers in Stenotrophomonas maltophilia DHHJ strain cells. Moreover, we used Co-IP with LC-MS/MS technology to search for proteins that interact with recombinant keratin monomers. We discovered TonB transports and molecular chaperones associating with the keratin monomer, which may play a crucial role in the transmembrane transport of keratin. Meanwhile, multiple proteases belonging to distinct families were identified as binding partners of keratin monomers, among which ATPases associated with diverse cellular activity (AAA+) family proteases are overrepresented. Four genes, including JJL50_15620, JJL50_17955 (TonB-dependent receptors), JJL50_03260 (ABC transporter ATP-binding protein), and JJL50_20035 (ABC transporter substrate-binding protein), were selected as representatives for determining their expressions under different culture conditions using qRT-PCR, and they were found to be upregulated in response to keratin degradation consistent with the data from RNA-seq and Co-IP. This study highlights the complexity of keratin biodegradation in S. maltophilia DHHJ, in which multiple pathways are involved such as protein folding, protein transport, and several protease systems. Our findings provide new insights into the mechanism of feather degradation.

The HSP40 family chaperone isoform DNAJB6b prevents neuronal cells from tau aggregation

BackgroundAlzheimer’s disease (AD) is the most common neurodegenerative disorder with clinical presentations of progressive cognitive and memory deterioration. The pathologic hallmarks of AD include tau neurofibrillary tangles and amyloid plaque depositions in the hippocampus and associated neocortex. The neuronal aggregated tau observed in AD cells suggests that the protein folding problem is a major cause of AD. J-domain-containing proteins (JDPs) are the largest family of cochaperones, which play a vital role in specifying and directing HSP70 chaperone functions. JDPs bind substrates and deliver them to HSP70. The association of JDP and HSP70 opens the substrate-binding domain of HSP70 to help the loading of the clients. However, in the initial HSP70 cycle, which JDP delivers tau to the HSP70 system in neuronal cells remains unclear.ResultsWe screened the requirement of a diverse panel of JDPs for preventing tau aggregation in the human neuroblastoma cell line SH-SY5Y by a filter retardation method. Interestingly, knockdown of DNAJB6, one of the JDPs, displayed tau aggregation and overexpression of DNAJB6b, one of the isoforms generated from the DNAJB6 gene by alternative splicing, reduced tau aggregation. Further, the tau bimolecular fluorescence complementation assay confirmed the DNAJB6b-dependent tau clearance. The co-immunoprecipitation and the proximity ligation assay demonstrated the protein–protein interaction between tau and the chaperone–cochaperone complex. The J-domain of DNAJB6b was critical for preventing tau aggregation. Moreover, reduced DNAJB6 expression and increased tau aggregation were detected in an age-dependent manner in immunohistochemical analysis of the hippocampus tissues of a mouse model of tau pathology.ConclusionsIn summary, downregulation of DNAJB6b increases the insoluble form of tau, while overexpression of DNAJB6b reduces tau aggregation. Moreover, DNAJB6b associates with tau. Therefore, this study reveals that DNAJB6b is a direct sensor for its client tau in the HSP70 folding system in neuronal cells, thus helping to prevent AD.

The Crustal Magmatic Structure Beneath the Denali Volcanic Gap Imaged by a Dense Linear Seismic Array

AbstractThe crustal structure in south‐central Alaska has been influenced by terrane accretion, flat slab subduction, and a modern strike‐slip fault system. Within the active subduction system, the presence of the Denali Volcanic Gap (DVG), a ∼400 km region separating the active volcanism of the Aleutian Arc to the west and the Wrangell volcanoes to the east, remains enigmatic. To better understand the regional tectonics and the nature of the volcanic gap, we deployed a month‐long north‐south linear geophone array of 306 stations with an interstation distance of 1 km across the Alaska Range. By calculating multi‐component noise cross‐correlation and jointly inverting Rayleigh wave phase velocity and ellipticity across the array, we construct a 2‐D shear wave velocity model along the transect down to ∼16 km depth. In the shallow crust, we observe low‐velocity structures associated with sedimentary basins and image the Denali fault as a narrow localized low‐velocity anomaly extending to at least 12 km depth. About 12 km, below the fold and thrust fault system in the northern flank of the Alaska Range, we observe a prominent low‐velocity zone with more than 15% velocity reduction. Our velocity model is consistent with known geological features and reveals a previously unknown low‐velocity zone that we interpret as a magmatic feature. Based on this feature's spatial relationship to the Buzzard Creek and Jumbo Dome volcanoes and the location above the subducting Pacific Plate, we interpret the low‐velocity zone as a previously unknown subduction‐related crustal magma reservoir located beneath the DVG.

Small heat shock proteins as modulators of cell death in Plasmodium falciparum parasites and its human host

Plasmodium falciparum, the predominant cause of severe malaria, thrives within both poikilotherm mosquitoes and homeotherm humans, navigating challenging temperature shifts during its life cycle. Survival in such varying environments necessitate the development of robust mechanisms, including a sophisticated protein folding system to mitigate proteopathy. The parasite needs to control the survival of its host cells which affects its chances of development and propagation. Central to this system are heat shock proteins (Hsps), among which small Hsps (sHsps) play pivotal roles in maintaining proteostasis (protein homeostasis). In both humans and P. falciparum, numerous sHsps have been identified, making them attractive candidates as biomarkers for diagnostic and drug development strategies. Evidence is accumulating suggesting that these sHsps participate in cell death processes, potentially influencing disease pathogenesis. Despite their significance, the precise functions of sHsps in P. falciparum’s adaptation to stress conditions remains largely unknown. Comparative structural analysis of sHsps between human and P. falciparum reveals species-specific variations. Despite conserved tertiary structures, unique motifs are found in parasite sHsps which may modulate specialised chaperone functions. This review discusses the conserved and distinctive motifs of sHsps from the human host and the parasite, offering insights into shared and unique attributes. These findings illuminate the potential for species-specific targeting of sHsps, as players in cell death processes that may foster innovative biomarker identification approaches. As malaria continues to ravage Sub-Saharan Africa, understanding the molecular intricacies guiding parasite survival are essential in the development of interventions with heightened efficacy against this global health crisis.

Optimization of IspSib stability through directed evolution to improve isoprene production.

Enzyme stability is often a limiting factor in the microbial production of high-value-added chemicals and commercial enzymes. A previous study by our research group revealed that the unstable isoprene synthase from Ipomoea batatas (IspSib) critically limits isoprene production in engineered Escherichia coli. Directed evolution was, therefore, performed in the present study to improve the thermostability of IspSib. First, a tripartite protein folding system designated as lac'-IspSib-'lac, which could couple the stability of IspSib to antibiotic ampicillin resistance, was successfully constructed for the high-throughput screening of variants. Directed evolution of IspSib was then performed through two rounds of random mutation and site-saturation mutation, which produced three variants with higher stability: IspSibN397V A476V, IspSibN397V A476T, and IspSibN397V A476C. The subsequent in vitro thermostability test confirmed the increased protein stability. The melting temperatures of the screened variants IspSibN397V A476V, IspSibN397V A476T, and IspSibN397V A476C were 45.1 ± 0.9°C, 46.1 ± 0.7°C, and 47.2 ± 0.3°C, respectively, each of which was higher than the melting temperature of wild-type IspSib (41.5 ± 0.4°C). The production of isoprene at the shake-flask fermentation level was increased by 1.94-folds, to 1,335 mg/L, when using IspSibN397V A476T. These findings provide insights into the optimization of the thermostability of terpene synthases, which are key enzymes for isoprenoid production in engineered microorganisms. In addition, the present study would serve as a successful example of improving enzyme stability without requiring detailed structural information or catalytic reaction mechanisms.IMPORTANCEThe poor thermostability of IspSib critically limits isoprene production in engineered Escherichia coli. A tripartite protein folding system designated as lac'-IspSib-'lac, which could couple the stability of IspSib to antibiotic ampicillin resistance, was successfully constructed for the first time. In order to improve the enzyme stability of IspSib, the directed evolution of IspSib was performed through error-PCR, and high-throughput screening was realized using the lac'-IspSib-'lac system. Three positive variants with increased thermostability were obtained. The thermostability test and the melting temperature analysis confirmed the increased stability of the enzyme. The production of isoprene was increased by 1.94-folds, to 1,335 mg/L, using IspSibN397V A476T. The directed evolution process reported here is also applicable to other terpene synthases key to isoprenoid production.

Role of inherited fault reactivation in accommodating multistage deformation in the southwestern margin of the Ulleung Basin, East Sea (Sea of Japan): Insights from 3D seismic interpretation

The southwestern margin of the Ulleung Basin, the East Sea (Sea of Japan), preserves complex structural and stratigraphic architectures produced by a multistage tectonic evolution in response to the Cenozoic convergence of the Indian and Pacific/Philippine Sea Plates to the Eurasian Plate. However, the origin, geometry, kinematics, and interrelationship of geological structures that evolved through the multistage tectonic deformation remain elusive, particularly regarding the role of structural inheritance in the evolution of the basin. Based on comprehensive 2D and 3D multichannel seismic reflection and well data, we present structural interpretations of regional-scale faults, folds, and growth strata in the southwestern margin of the Ulleung Basin, with a focus on inherited fault reactivation. In addition, a revisited deformation framework is proposed, involving back-arc extension/normal faulting (stage 1: ca. 23 to 15 Ma), positive inversion/reverse faulting (stage 2: 15 to 10.6 Ma), and strike-slip faulting/local transpression (stage 3: 10.6 Ma to present). Here, we illustrate how the reverse reactivation and propagation of segmented NE–SW normal faults and subsequent strike-slip movement have led to the complex structural and stratigraphic architectures presently evident in the study area. Notably, the final overprinting of a strike-slip deformation on the inherited NE–SW faults during deformation stage 3 has caused significantly damaged stepovers and tips, in which secondary faults and folds might control hydrocarbon migration/trapping and leakage. In this context, we suggest that the gentle antiformal Gorae Ⅰ structure is linked in origin to the Gorae Ⅴ structure, bearing a commercially viable gas trap as a detachment fold system formed by local transpression during deformation stage 3. Our comprehensive 3D structural seismic interpretation increases the understanding of Cenozoic multistage deformation, highlighting the impact of different tectonic drivers affecting the eastern marginal sea of the Eurasian Plate.

Radial and azimuthal seismic anisotropy in NW South America: Insights into crustal deformation and mantle flow using ambient noise and surface wave tomography

We illuminate the crustal and upper mantle structure of the northwestern corner of South America by mapping radial and azimuthal seismic anisotropy. Radial anisotropy is inferred from the discrepancy between VSV and VSH polarized S-velocities in horizontally propagating Rayleigh and Love waves, respectively. First, short-period (7–35 s) phase and group velocities are estimated from ambient noise cross-correlations, and long-period (40–170 s) group velocities are determined from fundamental-mode, surface-wave trains from earthquake sources at regional and teleseismic epicentral distances. Dispersion velocities are then tomographically inverted to develop maps of group velocity variation for periods between 7 and 170 s including azimuthal velocity dependence. We observe that positive anisotropy in the upper crust is related to thick Quaternary sequences in sedimentary basins, while negative anisotropy is found beneath active volcanoes and igneous-metamorphic terrains. Negative anisotropy features observed in the lower crust beneath the Eastern Cordillera suggest the existence of sill-like intrusions that penetrate the lower crust, thus supporting underplating mechanisms. Our study reveals SW-NE oriented fast axes of azimuthal anisotropy beneath the Eastern Cordillera, which strongly suggest the presence of shear zones within the fold and thrust belt system. Notably, the fast axes align parallel to the regional faults in the area, indicating a significant role in controlling faulting processes. Finally, we observe a wide trench-parallel zone of azimuthal anisotropy beneath the Nazca Plate, the Panama Block, and the Caribbean, which we associate with subslab mantle flow.