High-resolution carbon isotope stratigraphy of the Lower and Middle Ordovician succession of the Yangtze Platform, China

Variation in the relative abundance of the stable carbon isotopes has been widely used to correlate Ordovician marine successions over the past two decades. To date, only a few of studies of Ordovician carbon chemostratigraphy have been conducted in South China. Most of the previous studies in this field have focused on specific time intervals and/or events in the Middle and Upper Ordovician. The Lower and Middle Ordovician of the Yangtze Platform is typically represented by a sedimentary succession dominated by carbonate rocks, which is ideal for studying the carbon chemostratigraphy. Three sections spanning the Nantsinkuan/Lunshan, Fenhsiang, Hunghuayuan, and Dawan/Zitai formations, corresponding to the TremadocianâDapingian in age, have been sampled for high-resolution δ13C chemostratigraphy. Our new δ13C data reveal five tie-points with the potential for global correlation: (1) a positive δ13C excursion in the lower Nantsinkuan Formation within the Tremadocian Rossodus manitouensis Zone; (2) an excursion with two peaks roughly within the late Tremadocian Paltodus âdeltiferâ Zone; (3) a positive δ13C shift in the lower Hunghuayuan Formation, within the early Floian Serratognathus diversus Zone; (4) a gradual positive δ13C shift in the late Floian, ranging from the uppermost S. diversus Zone to the basal Oepikodus evae Zone; (5) a minor negative shift in the lower Dawan/Zitai Formation, within the early Dapingian Baltoniodus triangularis Zone. These excursions are herein used for correlation of the Yangtze Platform strata with successions from South China, North China, the Argentine Precordillera, North America and Baltica. From a palaeogeographical perspective, the Gudongkou, Xiangshuidong and Daling sections represent depositional environments along an inner to outer ramp profile. The δ13C data from these sections show successively heavier (higher) δ13C values with increasing depositional depth, which can be interpreted as due to remineralization of organic carbon within the carbonate rocks formed in the shallow-water environment

Data from: Katian (Late Ordovician) trilobites of the North Qilian Mountains and their palaeogeographical implications for the Proto-Tethys Archipelagic Ocean (PTAO)

<p class="MsoNormal"><span>Trilobites from the middle Koumenzi Formation (Katian, Upper Ordovician) of the North Qilian Mountains, Menyuan, northeastern Qinghai Province are systematically documented for the first time. The fauna consists of five families, seven genera and seven species, amongst which one is new (</span><em><span>Remopleurides</span> <span>zhangi</span> </em><span>sp. nov.), showing a close relationship to those of the Kazakh terranes (such as Chu-Ili terrane, Chingiz-Tarbagatai area and KNNTS (Karatau-Naryn and North-Tien Shan Microcontinents)), North China and Laurentia palaeoplates during the Katian (Late Ordovician). The cluster and Non-metric Multidimensional Scaling analyses of the Middle<span class="fontstyle01">–Late Ordovician (</span>late Darriwilian<span class="fontstyle01">–</span>Katian<span class="fontstyle01">) trilobite faunas with 299 genera or subgenera from 46 horizons of 37 areas, provide valuable information for the palaeogeographical reconstruction of the </span>Proto-Tethys Archipelagic Ocean (PTAO) of this interval. The Qilian terrane and adjacent areas are essential components of the PTAO, some of which include the Qilian terrane (QT), the North Qilian Mountains area (NQ), the Altun faulted terrane (AFT), the Hexi Corridor area (HX) and the East Qinling terrane (EQT). Their relative positions within the PTAO are inferred by the palaeobiogeography of trilobite faunas. Based on further discussions on the spatiotemporal distribution of those faunas<span class="fontstyle01">, the </span></span><em><span>Pliomerina</span></em><span> and/or </span><em><span>Sinocybele</span> </em><span>Province of the Middle<span class="fontstyle01">–Late Ordovician (</span>late Darriwilian<span class="fontstyle01">–</span>Katian<span class="fontstyle01">) age is defined as a trilobite faunal province of the PTAO. </span>Moreover, a distinct faunal subprovince, essentially comprised of the South China Palaeoplate and its neighbours (e.g. Tarim, Annamia, Sibuma, East Qinling, Turkestan-Alai and probably Talesh), might be surrounded by the equatorial cold-water tongue.</span></p><p>Funding provided by: Chinese Academy of Sciences<br>Crossref Funder Registry ID: https://ror.org/034t30j35<br>Award Number: XDB26000000</p><p>Funding provided by: National Natural Science Foundation of China<br>Crossref Funder Registry ID: https://ror.org/01h0zpd94<br>Award Number: 41972011</p><p>Funding provided by: State Key Laboratory of Palaeobiology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, CAS)*<br>Crossref Funder Registry ID: <br>Award Number: 213123</p><p>Funding provided by: National Natural Science Foundation of China<br>Crossref Funder Registry ID: https://ror.org/01h0zpd94<br>Award Number: 41972015</p><p>Funding provided by: National Natural Science Foundation of China<br>Crossref Funder Registry ID: https://ror.org/01h0zpd94<br>Award Number: 42072005</p><p>Funding provided by: National Natural Science Foundation of China<br>Crossref Funder Registry ID: https://ror.org/01h0zpd94<br>Award Number: 42072007</p><p>Funding provided by: National Natural Science Foundation of China<br>Crossref Funder Registry ID: https://ror.org/01h0zpd94<br>Award Number: 42102130</p&gt

A distinct expression pattern of cyclin K in mammalian testes suggests a functional role in spermatogenesis.

Germ cell and embryonic stem cells are inextricably linked in many aspects. Remarkably both can generate all somatic cell types in organisms. Yet the molecular regulation accounting for these similarities is not fully understood. Cyclin K was previously thought to associate with CDK9 to regulate gene expression. However, we and others have recently shown that its cognate interacting partners are CDK12 and CDK13 in mammalian cells. We further demonstrated that cyclin K is essential for embryonic stem cell maintenance. In this study, we examined the expression of cyclin K in various murine and human tissues. We found that cyclin K is highly expressed in mammalian testes in a developmentally regulated manner. During neonatal spermatogenesis, cyclin K is highly expressed in gonocytes and spermatogonial stem cells. In adult testes, cyclin K can be detected in spermatogonial stem cells but is absent in differentiating spermatogonia, spermatids and spermatozoa. Interestingly, the strongest expression of cyclin K is detected in primary spermatocytes. In addition, we found that cyclin K is highly expressed in human testicular cancers. Knockdown of cyclin K in a testicular cancer cell line markedly reduces cell proliferation. Collectively, we suggest that cyclin K may be a novel molecular link between germ cell development, cancer development and embryonic stem cell maintenance

The record of early Silurian climate changes from South China and Baltica based on integrated conodont biostratigraphy and isotope chemostratigraphy

New conodont and stable isotope data are presented from the classical Baizitian section in the Yanbian County of Sichuan Province, South China. The Telychian to Sheinwoodian strata were sampled and studied for carbon isotope stratigraphy and conodont biostratigraphy. The paired δ13Ccarb and δ13Corg data reveal a pronounced positive excursion, the Manitowoc carbon isotope excursion (Manitowoc CIE, ‘Manitowoc Excursion’) spanning the upper Pterospathodus eopennatus Zone and the lower Pterospathodus amorphognathoides amorphognathoides Superzone, with an increase of ca. 2‰ in δ13Ccarb and ca. 5‰ in δ13Corg. Well-bracketed by conodont biostratigraphy, the Manitowoc CIE is an essential tie-point for correlation between the Baizitian succession and the Telychian strata of Baltica and Laurentia. Our new δ13Ccarb and δ13Corg data imply that the carbon isotope excursion previously recognized as the ‘Ireviken Excursion’ (Early Sheinwoodian Carbon Isotope Excursion) at Baizitian should be revised as being the Manitowoc CIE. The Δ13C data presented in this study further suggest a slight concurrent drop of atmospheric CO2, and thus add evidence for a perturbation of the global carbon cycle during the middle Telychian. Based on the combined information from the conodont apatite oxygen isotope records from Estonia and the significant stratigraphic gaps recognized at the Baizitian section, we propose that the latter stratigraphic gaps should correlate with the Telychian Valgu and the early Sheinwoodian glaciation

Cyclin K is required for proliferation of testicular cancer cells.

<p>A) Knockdown of CycK by either scrambled (scr) or two different shRNA constructs (mK-1 and mK-2). Cells were grown for four days after knockdown, and collected for protein blot analyses. B) Crystal violet staining of cells four days after knockdown. C) Quantitation of cells in B) from three independent experiments. Error bars represent SD. Scale bar: 500 µm.</p

Expression of cyclin K in human tissues.

<p>A) Expression of CycK in liver, brain and muscle tissues of an 18-year-old male. B) Expression of CycK in testes of three individual with different ages. Scale bar: 20 µm.</p

Cyclin K is highly expressed in murine testes.

<p>A) The level of CycK mRNA was determined by qPCR. Expression of CycK was normalized to that of Gapdh in three independent experiments. CycK expression in stomach was arbitrarily assigned to be one, and expression levels in other tissues were normalized to that of stomach. Error bars represent SD. B) Protein blot analysis of CycK expression in different tissues. Total tissue lysates were separated by SDS-PAGE and probed by the indicated antibodies. Representative blot of three independent experiments was shown. C) Tissue sections from 2-month-old mice were stained by IHC with anti-CycK antibodies followed by staining with hematoxylin. Upper panel, detection of CycK in testes. Preincubation with epitope peptides eliminated the signal (left). Secondary antibodies alone did not generate any signal (middle). Cyck expression could be seen in different cell types in seminiferous tubules (right). Lower panel,CycK expression in various tissues. In each case, second antibodies alone (2nd) did not produce detectable signals. Of note, staining was carried out on the same day to allow semi-quantitative comparisons of CycK expression levels. Representative results from four independent experiments were shown. Scale bar: 20 µm.</p

Expression of cyclin K is developmentally regulated during spermatogenesis.

<p>A) Schematic presentation of cell types and key events during neonatal and adult spermatogenesis in mice. B) Expression of CycK detected by IHC at different stages of spermatogenesis. Representative results from four independent experiments were shown. Asterisks denote spermatocytes. Scale bar: 20 µm.</p

Cyclin K is highly expressed in germ cell compartment.

<p>A) Expression of CycK and vimentin at different stages of spermatogenesis. Vimentin is a marker for Sertoli cells. Representative results from two independent experiments were shown. Arrows denote Sertoli cells. B) Detection of CycK and vimentin on the same region of seminiferous tubules. Vimentin was detected by immunofluorescence, followed by detection of CycK by IHC. DNA was visualized by DAPI staining. C) Expression of CycK could be detected in Plzf-positive spermatogonial stem cells. Scale bar: 20 µm.</p