Testing the mantle plume hypothesis: An IODP effort to drill into the Kamchatka-Okhotsk Sea system

The great mantle plume debate (GPD) has been going on for ∼15 years (Foulger and Natland, 2003; Anderson, 2004; Niu, 2005; Davies, 2005; Foulger, 2005; Campbell, 2005; Campbell and Davies, 2006), centered on whether mantle plumes exist as a result of Earth’s cooling or whether their existence is purely required for convenience in explaining certain Earth phenomena (Niu, 2005). Despite the mounting evidence that many of the so-called plumes may be localized melting anomalies, the debate is likely to continue. We recognize that the slow progress of the debate results from communication difficulties. Many debaters may not truly appreciate (1) what the mantle plume hypothesis actually is, and (2) none of the petrological, geochemical and geophysical methods widely used can actually provide smoking-gun evidence for or against mantle plume hypothesis. In this short paper, we clarify these issues, and elaborate a geologically effective approach to test the hypothesis. According to the mantle plume hypothesis, a thermal mantle plume must originate from the thermal boundary layer at the core-mantle boundary (CMB), and a large mantle plume head is required to carry the material from the deep mantle to the surface. The plume head product in ocean basins is the oceanic plateau, which is a lithospheric terrane that is large (1000’s km across), thick (>200 km), shallow (2–4 km high above the surrounding seafloors), buoyant (∼1% less dense than the surrounding lithosphere), and thus must be preserved in the surface geology (Niu et al., 2003). The Hawaiian volcanism has been considered as the surface expression of a type mantle plume, but it does not seem to have a (known) plume head product. If this is true, the Hawaiian mantle plume in particular and the mantle plume hypothesis in general must be questioned. Therefore, whether there is an oceanic plateau-like product for the Hawaiian volcanism is key to testing the mantle plume hypothesis, and the Kamchatka-Okhotsk Sea basement is the best candidate to find out if it is indeed the Hawaiian mantle plume head product or not (Niu et al., 2003; Niu, 2004)

Local earthquake seismic tomography of the Southernmost Mariana subduction zone

We employed seismic tomography to examine the velocity structure of the upper mantle in the Southernmost Mariana subduction zone. Our study focuses on data collected during a six-month experiment from 15 December 2016 to 12 June 2017, using 11 ocean bottom seismometers. By examining over 3700 local arrival times, we are able to determine the three-dimensional Vp and Vs structure. The subducting slab in this region displays a P- and S-wave velocity 2~6% higher than normal mantle and a lower Vp/Vs, with an average dip of 45° at depths ranging from 50 to 100 km. Additionally, our velocity images also shed new lights to the velocity anomalies of the mantle wedge region on top of the subducting slab, from the trench to the remnant arc. We observed slower velocity anomalies in the mantle wedge beneath the Southwest Mariana Rift, the West Mariana Ridge, and the forearc. In the outer forearc, a low-velocity anomaly is observed at depths shallower than 50 km, indicating mantle serpentinization and the presence of water. Additionally, a melt production region is observed beneath the central part of the forearc block at a depth of 40–60 km suggesting the possibility of melting processes in this region

Administering plasmid DNA encoding tumor vessel-anchored IFN-α for localizing gene product within or into tumors

Tumor-targeted gene delivery has been intensively studied in the field of gene therapy, but no attention has been given to targeting the therapeutic gene products, which are transcribed and translated from the injected genes, into tumors. Targeting immune stimulatory gene products into tumors is the key to triggering tumor-specific CD8+ T-cell responses and reducing systemic toxicity. To target the gene products generated from the injected genes into tumors, genes encoding the tumor-targeted fusion gene product were generated and administered locally and systemically via electroporation. As anticipated, administration of a therapeutic gene encoding IFN-α and the tumor vessel-targeted peptide CDGRC fusion gene product minimizes the leakage of immunostimulatory cytokine from tumors into the blood circulation, increases the infiltration of CD8+ T cells into tumors, induces a high magnitude of cytotoxic T-cell lysis (CTL) activity, and reduces tumor vessel density. As a result, tumor growth was more significantly inhibited by administering the IFN-α-CDGRC gene than by administering the wild-type IFN-α gene. The same result was obtained with the systemic administration of the tumor-targeted IFN-α gene. This gene product-based tumor-targeted gene therapy approach could complement any other tumor-targeted gene delivery method for improving tumor-targeting efficiency

Prolonged post-rift magmatism on highly extended crust of divergent continental margins (Baiyun Sag, South China Sea)

Three-dimensional (3D) seismic, borehole and geochemical data reveal a prolonged phase of post-rift magmatism on highly extended crust of the Baiyun Sag, South China Sea. Two volcanic complexes are identified and described in the context of continental rifting and diachronous continental breakup of the South China Sea. Biostratigraphic data from exploration wells BY7-1 and BY2, complemented by K–Ar datings from core samples, confirm that magmatic activity in the Baiyun Sag occurred in two main stages: (1) a first episode at the base of the Miocene (23.8 Ma); and (2) a second episode occurring at the end of the Early Miocene (17.6 Ma). The relative location of volcanic complexes in the Baiyun Sag, and their stratigraphic position, reveals prolonged magmatism inboard of the ocean–continent transition zone during continental breakup. We suggest that magmatism in the Baiyun Sag reflects progressive continental breakup in the South China Sea, with the last volcanic episode marking the end of a breakup sequence representing the early post-rift tectonic events associated with the continental breakup process. Seismic and borehole data from this breakup sequence records diachronous magma emplacement and complex changes in depositional environments during continental breakup

Recurrent slope failure enhancing source rock burial depth and seal unit competence in the Pearl River Mouth Basin, offshore South China Sea

High-quality 3-D seismic data are used to assess the significance of mass-transport deposits (MTDs) to the evolution of the Pearl River Mouth Basin (South China Sea). Basal shear surfaces and lateral margins of seven recurrent MTDs are mapped to reveal a general NE-SW transport direction throughout the Late Miocene-Quaternary. A key result of our analysis is the perceived relationship between the recurrence of slope instability in the study area and the Dongsha Tectonic Event. Using borehole data to constrain the ages of interpreted MTDs, we show that tectonic uplift in the northern South China Sea led to slope oversteepening in the Late Miocene (between 10.5 Ma and 5.5 Ma), preconditioning it to fail recurrently for more than 10 Ma. Interpreted MTDs are shown to enhance burial depths of source and reservoir units, and improve seal competence in lower-slope areas. Conversely, upper slope regions record important erosion and reduced sealing capacity in Late Cenozoic strata. As a result, we postulate that the thickness variations imposed by MTDs on Late Miocene-Quaternary strata have important implications to petroleum plays in the South China Sea

Genome-Wide Identification and Evaluation of New Reference Genes for Gene Expression Analysis Under Temperature and Salinity Stresses in Ciona savignyi

Rapid adaptation/accommodation to changing environments largely contributes to maximal survival of invaders during biological invasions, usually leading to success in crossing multiple barriers and finally in varied environments in recipient habitats. Gene expression is one of the most important and rapid ways during responses to environmental stresses. Selection of proper reference genes is the crucial prerequisite for gene expression analysis using the common approach, real-time quantitative PCR (RT-qPCR). Here we identified eight candidate novel reference genes from the RNA-Seq data in an invasive model ascidian Ciona savignyi under temperature and salinity stresses. Subsequently, the expression stability of these eight novel reference genes, as well as other six traditionally used reference genes, was evaluated using RT-qPCR and comprehensive tool RefFinder. Under the temperature stress, two traditional reference genes, ribosomal proteins S15 and L17 (RPS15, RPL17), and one novel gene Ras homolog A (RhoA), were recommended as the top three stable genes, which can be used to normalize target genes with a high and moderate expression level, respectively. Under the salinity stress, transmembrane 9 superfamily member (TMN), MOB kinase activator 1A-like gene (MOB) and ubiquitin-conjugating enzyme (UBQ2) were suggested as the top three stable genes. On the other hand, several commonly used reference genes such as α-tubulin (TubA), β-tubulin (TubB) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) showed unstable expressions, thus these genes should not be used as internal controls for gene expression analysis. We also tested the expression level of an important stress response gene, large proline-rich protein bag6-like gene (BAG) using different reference genes. As expected, we observed different results and conclusions when using different normalization methods, thus suggesting the importance of selection of proper reference genes and associated normalization methods. Our results provide a valuable reference gene resource for the normalization of gene expression in the study of environmental adaptation/accommodation during biological invasions using C. savignyi as a model

Distribution patterns of dinoflagellate communities along the Songhua River

Background Dinoflagellates have the potential to pose severe ecological and economic damages to aquatic ecosystems. It is therefore largely needed to understand the causes and consequences of distribution patterns of dinoflagellate communities in order to manage potential environmental problems. However, a majority of studies have focused on marine ecosystems, while the geographical distribution patterns of dinoflagellate communities and associated determinants in freshwater ecosystems remain unexplored, particularly in running water ecosystems such as rivers and streams. Methods Here we utilized multiple linear regression analysis and combined information on species composition recovered by high-throughput sequencing and spatial and environmental variables to analyze the distribution patterns of dinoflagellate communities along the Songhua River. Results After high-throughput sequencing, a total of 490 operational taxonomic units (OTUs) were assigned to dinoflagellates, covering seven orders, 13 families and 22 genera. Although the sample sites were grouped into three distinctive clusters with significant difference (p  0.05). Among all 24 environmental factors, two environmental variables, including NO3-N and total dissolved solids (TDS), were selected as the significantly influential factors (p < 0.05) on the distribution patterns of dinoflagellate communities based on forward selection. The redundancy analysis (RDA) model showed that only a small proportion of community variation (6.1%) could be explained by both environmental (NO3-N and TDS) and dispersal predictors (watercourse distance) along the River. Variance partitioning revealed a larger contribution of local environmental factors (5.85%) than dispersal (0.50%) to the total variation of dinoflagellate communities. Discussion Our findings indicated that in addition to the two quantifiable processes in this study (species sorting and dispersal), more unquantifiable stochastic processes such as temporal extinction and colonization events due to rainfall may be responsible for the observed geographical distribution of the dinoflagellate community along the Songhua River. Results obtained in this study suggested that deeper investigations covering different seasons are needed to understand the causes and consequences of geographical distribution patterns of dinoflagellate biodiversity in river ecosystems

Genetic testing of PAX8 mutations associated with thyroid dysgenesis in Chinese congenital hypothyroidism patients

Introduction: Thyroid dysgenesis (TD) is the main cause of congenital hypothyroidism (CH), affecting nearly 1 in 2000–3000 newborns worldwide, as the most common neonatal endocrine disorder. Paired box gene 8 (PAX8), expressed during all stages of thyroid follicular cell, plays a key role in thyroid morphogenesis by a complex regulatory network. In conclusion, the genetic mechanism of PAX8 mutant in TD is still ambiguous; therefore, further research is needed. Material and methods: Blood samples were collected from 289 TD patients in Shandong Province, China. Genomic DNA was extracted from peripheral blood. All the exons of PAX8 along with their exon-intro boundaries were amplified by PCR and analysed by Sanger sequencing. Results: We identified three novel PAX8 nonsense mutations in three patients by sequence analysis of PAX8: Patient 1 (c.285C&gt;G, p.Tyr95Ter), Patient 2 (c.747T&gt;G, p.Tyr249Ter), and Patient 3 (c.786C&gt;A, p.Tyr262Ter). All the three patients carrying PAX8 variants had obvious clinical phenotypes of thyroid anomaly, such as hypoplasia and athyreosis. Conclusion: We conducted the largest worldwide PAX8 mutation screening so far in TD patients. Three presumably pathogenic PAX8 mutations were detected in 289 TD cases for the first time, showing the mutation rate of PAX8 is 1.04% in Chinese TD patients. In addition, our study expands the gene mutation spectrum of TD