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1. Upper Crustal Structure and Magmatism in Southwest Washington: V _p , V _s , and V _p / V _s Results From the iMUSH Active‐Source Seismic Experiment

   https://doi.org/10.1029/2018JB016203  

   Kiser, E. ; Levander, A. ; Zelt, C. ; Schmandt, B. ; Hansen, S. ( July 2019 , Journal of Geophysical Research: Solid Earth)

   Structural details of the crust play an important role in controlling the distribution of volcanic activity in arc systems. In southwest Washington, several different regional structures associated with accretion and magmatism have been invoked to explain the broad distribution of Cascade volcanism in this region. In order to image these regional structures in the upper crust, Pg and Sg travel times from the imaging Magma Under St. Helens (iMUSH) active‐source seismic experiment are inverted forV_p,V_s, andV_p/V_smodels in the region surrounding Mount St. Helens. Several features of these models provide new insights into the regional structure of the upper crust. A large section of the Southern Washington Cascades Conductor is imaged as a lowV_p/V_sanomaly that is inferred to represent a broad sedimentary/metasedimentary sequence that composes the upper crust in this region. The accreted terrane Siletzia is imaged west of Mount St. Helens as north/south trending highV_pandV_p/V_sbodies. TheV_p/V_smodel shows relatively highV_p/V_sregions near Mount St. Helens and the Indian Heaven Volcanic Field, which could be related to the presence of magmatic fluids. Separating these two volcanic regions below 6‐km depth is a northeast trending series of highV_pandV_sbodies. These bodies have the same orientation as several volcanic/magmatic features at the surface, including Mountmore »St. Helens and Mount Rainier, and it is argued that these high‐velocity features are a regional‐scale group of intrusive bodies associated with a crustal weak zone that focuses magma ascent.

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2. In‐Situ V _p / V _s Reveals Fault‐Zone Material Variation at the Westernmost Gofar Transform Fault, East Pacific Rise

   https://doi.org/10.1029/2022JB025310  

   Liu, Tianze ; Gong, Jianhua ; Fan, Wenyuan ; Lin, Guoqing ( March 2023 , Journal of Geophysical Research: Solid Earth)

   Ocean transform faults often generate characteristic earthquakes that repeatedly rupture the same fault patches. The westernmost Gofar transform fault quasi‐periodically hosts ∼M6 earthquakes every ∼5 years, and microseismicity suggests that the fault is segmented into five distinct zones, including a rupture barrier zone that may have modulated the rupture of adjacentM6 earthquakes. However, the relationship between the systematic slip behavior of the Gofar fault and the fault material properties is still poorly known. Specifically, the role of pore fluids in regulating the slip of the Gofar fault is unclear. Here, we use differential travel times between nearby earthquakes to estimate the in‐situV_p/V_sof the fault‐zone materials. We apply this technique to the dataset collected by an ocean‐bottom‐seismometer network deployed around the Gofar fault in 2008, which recorded abundant microearthquakes, and find a moderateV_p/V_sof 1.75–1.80 in the rupture barrier zone and a lowV_p/V_sof 1.61–1.69 in the down‐dip edge of the 2008M6 rupture zone. This lateral variation inV_p/V_smay be caused by both pore fluids and chemical alteration. We also find a 5%–10% increase inV_p/V_sin the barrier zone during the 9 months before the mainshock. This increase may have been caused by fluid migrations or slip transients in the barrier zone.
3. Use of the high‐affinity phosphate transporter gene, pstS , as an indicator for phosphorus stress in the marine diazotroph Crocosphaera watsonii ( Chroococcales , Cyanobacteria )

   https://doi.org/10.1111/jpy.12863  

   Pereira, Nicole ; Shilova, Irina N. ; Zehr, Jonathan P. ; Roleda, ed., M. ( May 2019 , Journal of Phycology)

   The marine diazotrophCrocosphaera watsoniiprovides fixed carbon (C) and nitrogen (N) to open‐ocean regimes, where nutrient deficiency controls productivity. The growth ofCrocosphaeracan be limited by low phosphorus (P) concentrations in these oligotrophic environments. Biomarkers such as the high‐affinityABCtransporter phosphate‐binding gene,pstS, are commonly used to monitor when such organisms are under P stress; however, transcriptional regulation of these markers is often complex and not well‐understood. In this study, we interrogated changes inpstStranscript levels inC. watsoniicells under P starvation, and in response to added dissolved inorganic phosphorus (DIP), dissolved organic phosphorus (DOP), and changing light levels. We observed elevated relativepstStranscript levels inC. watsoniiWH8501 atDIPconcentrations below 60 and above 20 nmol · L⁻¹. Transcript levels were suppressed by both inorganic and bioavailable organic phosphorus; however, the P stress response was more sensitive toDIPthanDOPsources. Increasing light intensity resulted in increased relativepstStranscript abundances independently of low external P, and seemed to exacerbate the physiological effects of P stress. The variable response to different P compounds and rapid and transient influence of high light onpstStranscript abundances suggests thatpstSis an indicator of internal P status inCrocosphaera.
4. Paludicola gen. nov. and Revision of the Species Formerly in Batrachospermum Section  Turfosa (Batrachospermales, Rhodophyta)

   https://doi.org/10.1111/jpy.13001  

   Vis, Morgan L. ; Lee, Janina ; Eloranta, Pertti ; Chapuis, Iara S. ; Lam, Daryl W. ; Necchi, Jr., Orlando ; Oliveira, ed., M. C. ( May 2020 , Journal of Phycology)

   Since the first phylogenetic study of the order Batrachospermales,Batrachospermumwas shown to be paraphyletic. Subsequently, sections of the genus have been methodically investigated usingDNAsequences and morphology in order to propose new genera and delineate species.BatrachospermumsectionTurfosais the last section with multiple species yet to be examined. New sequence data of specimens from Europe and the United States were combined with the sparse sequence data already available. Phylogenetic analyses usingrbcL andCOI‐5P sequences showed this section to be a well‐supported clade, distinct fromBatrachospermumsectionBatrachospermumand its segregate genera. Section Turfosais raised to the generic rank asPaludicolagen. nov. Substantial genetic variation within the genus was discovered and 12 species are recognized based onDNAsequence data as well as morphological characters and geographic distribution. The following morphological characters were applied to distinguish species: branching pattern (pseudodichotomous or irregular), whorl size (reduced or well developed), primary fascicles (curved or straight), spermatangia origin (primary or secondary fascicles), and carposporophyte arrangement (loose or dense). Previously published species were transferred to the new genus:P. turfosa,P. keratophyta,P. orthosticha,P. phangiae,andP. periploca. Seven new species are proposed as follows:P. groenbladiifrom Europe;P. communis,P. johnhallii, andP. leafensisfrom North America; andP. aquanigra,P. diamantinensis, andP. turfosiformisfrom Brazil. In addition, three unsequenced species in the section,P. bakarensis,P. gombakensis, andP. tapirensis, were transferred to the new genus.
5. Comparative genomics of Rhizophagus irregularis , R. cerebriforme , R. diaphanus and Gigaspora rosea highlights specific genetic features in Glomeromycotina

   https://doi.org/10.1111/nph.15687  

   Morin, Emmanuelle ; Miyauchi, Shingo ; San Clemente, Hélène ; Chen, Eric C. H. ; Pelin, Adrian ; de la Providencia, Ivan ; Ndikumana, Steve ; Beaudet, Denis ; Hainaut, Mathieu ; Drula, Elodie ; et al ( February 2019 , New Phytologist)

   Glomeromycotina is a lineage of early diverging fungi that establish arbuscular mycorrhizal (AM) symbiosis with land plants. Despite their major ecological role, the genetic basis of their obligate mutualism remains largely unknown, hindering our understanding of their evolution and biology.

   We compared the genomes of Glomerales (Rhizophagus irregularis,Rhizophagus diaphanus,Rhizophagus cerebriforme) and Diversisporales (Gigaspora rosea) species, together with those of saprotrophic Mucoromycota,to identify gene families and processes associated with these lineages and to understand the molecular underpinning of their symbiotic lifestyle.

   Genomic features in Glomeromycotina appear to be very similar with a very high content in transposons and protein‐coding genes, extensive duplications of protein kinase genes, and loss of genes coding for lignocellulose degradation, thiamin biosynthesis and cytosolic fatty acid synthase. Most symbiosis‐related genes inR. irregularisandG. roseaare specific to Glomeromycotina. We also confirmed that the present species have a homokaryotic genome organisation.

   The high interspecific diversity of Glomeromycotina gene repertoires, affecting all known protein domains, as well as symbiosis‐related orphan genes, may explain the known adaptation of Glomeromycotina to a wide range of environmental settings. Our findings contribute to an increasingly detailed portrait of genomic features defining the biology ofAMfungi.