Biotic response of plankton communities to Middle to Late Miocene monsoon wind and nutrient flux changes in the Oman margin upwelling zone

Understanding past dynamics of upwelling cells is an important aspect of assessing potential upwelling changes in future climate change scenarios. Our present understanding of nutrient fluxes throughout the world's oceans emphasizes the importance of intermediate waters transporting nutrients from the Antarctic divergence into the middle and lower latitudes. These nutrient-rich waters fuel productivity within wind-driven upwelling cells in all major oceans. One such upwelling system is located along the Oman margin in the western Arabian Sea (WAS). Driven by cross-hemispheric winds, the WAS upwelling zone's intense productivity led to the formation of one of the most extensive oxygen minimum zones known today. In this study covering the Middle to Late Miocene at Ocean Drilling Program (ODP) Site 722, we investigate the inception of upwelling-derived primary productivity. This study presents new plankton assemblage data in the context of existing model- and data-based evidence constraining the tectonic and atmospheric boundary conditions for upwelling in the WAS. With this research, we build upon the original planktonic foraminifer-based research by Dick Kroon in 1991 as part of his research based on the ODP LEG 117. We show that monsoonal winds likely sustained upwelling since the emergence of the Arabian Peninsula after the Miocene Climatic Optimum (MCO) ∼ 14.7 Ma, with fully monsoonal conditions occurring since the end of the Middle Miocene Climatic Transition (MMCT) at ∼ 13 Ma. However, changing nutrient fluxes through Antarctic Intermediate and sub-Antarctic Mode Waters (AAIW/SAMW) were only established after ∼ 12 Ma. Rare occurrences of diatom frustules correspond to the maximum abundances of Reticulofenestra haqii and Reticulofenestra antarctica, indicating higher upwelling-derived nutrient levels. By 11 Ma, diatom abundance increases significantly, leading to alternating diatom blooms and high-nutrient-adapted nannoplankton taxa. These changes in primary producers are also well reflected in geochemical proxies with increasing δ15Norg. values (&gt; 6 ‰) and high organic carbon accumulation. These proxies provide further independent evidence for high productivity and the onset of denitrification simultaneously. Our multi-proxy-based evaluation of Site 722 primary producers provides evidence for a stepwise evolution of Middle to Late Miocene productivity in the western Arabian Sea for the first time. The absence of a clear correlation with existing deep marine climate records suggests that both local wind patterns and intermediate water nutrient changes likely modulated productivity in the western Arabian Sea during the Middle to Late Miocene. Finally, we show that using a multi-proxy record provides novel insights into how plankton responded to changing nutrient conditions through time in a monsoon-wind-driven upwelling zone.</p

Early Miocene Intensification of the North African Hydrological Cycle: Multi-Proxy Evidence From the Shelf Carbonates of Malta

During the Miocene (23.0–5.3 Ma) North Africa experienced both humid and arid intervals, but the underlying cause of these transitions is unknown. Earth's climate was characterized by a unipolar icehouse with a dynamic Antarctic ice sheet, which may have influenced regional hydrology through atmospheric teleconnections. However, the Miocene also witnessed the restriction of the Mesopotamian Seaway, which may have had significant climatic impacts. The Maltese il-Blata section (Central Mediterranean) comprises Late Oligocene to Early Miocene marine deposits previously used to constrain the timing of the Mesopotamian Seaway restriction using the εNd tracer. The location of this section also makes it sensitive to climatic changes in the North African region, and biogeochemical changes in the central Mediterranean. Here, we present lithological and geochemical records of the il-Blata section. We find a marked shift in lithology and an increase in sedimentation rate coeval with the Early Miocene (∼19–20 Ma) restriction of the Mesopotamian Seaway. Concomitant changes in bulk sediment CaCO3, Sr/Ca, K/Al, Ti/Al, Zr/Al, and Si/Ti support a major humid climate transition and associated intensification of river systems over western North Africa. We propose that these changes in North African hydroclimate reflect either a tipping point effect in a gradually warming global climate, or are the result of the initial restriction of the Mesopotamian Seaway, perhaps through consequent changes in Atlantic Meridional Overturning Circulation and the West African Monsoon. We also suggest the restriction of the Mesopotamian Seaway inhibited phosphorite deposition at low latitudes

GTP binding and intramolecular regulation by the ROC domain of Death Associated Protein Kinase 1

The ROCO proteins are a family of large, multidomain proteins characterised by the presence of a Ras of complex proteins (ROC) domain followed by a COR, or C-terminal of ROC, domain. It has previously been shown that the ROC domain of the human ROCO protein Leucine Rich Repeat Kinase 2 (LRRK2) controls its kinase activity. Here, the ability of the ROC domain of another human ROCO protein, Death Associated Protein Kinase 1 (DAPK1), to bind GTP and control its kinase activity has been evaluated. In contrast to LRRK2, loss of GTP binding by DAPK1 does not result in loss of kinase activity, instead acting to modulate this activity. These data highlight the ROC domain of DAPK1 as a target for modifiers of this proteins function, and casts light on the role of ROC domains as intramolecular regulators in complex proteins with implications for a broad range of human diseases

Cytoskeletal protein kinases: titin and its relations in mechanosensing

Titin, the giant elastic ruler protein of striated muscle sarcomeres, contains a catalytic kinase domain related to a family of intrasterically regulated protein kinases. The most extensively studied member of this branch of the human kinome is the Ca2+–calmodulin (CaM)-regulated myosin light-chain kinases (MLCK). However, not all kinases of the MLCK branch are functional MLCKs, and about half lack a CaM binding site in their C-terminal autoinhibitory tail (AI). A unifying feature is their association with the cytoskeleton, mostly via actin and myosin filaments. Titin kinase, similar to its invertebrate analogue twitchin kinase and likely other “MLCKs”, is not Ca2+–calmodulin-activated. Recently, local protein unfolding of the C-terminal AI has emerged as a common mechanism in the activation of CaM kinases. Single-molecule data suggested that opening of the TK active site could also be achieved by mechanical unfolding of the AI. Mechanical modulation of catalytic activity might thus allow cytoskeletal signalling proteins to act as mechanosensors, creating feedback mechanisms between cytoskeletal tension and tension generation or cellular remodelling. Similar to other MLCK-like kinases like DRAK2 and DAPK1, TK is linked to protein turnover regulation via the autophagy/lysosomal system, suggesting the MLCK-like kinases have common functions beyond contraction regulation

Active Pin1 is a key target of all-trans retinoic acid in acute promyelocytic leukemia and breast cancer

A common key regulator of oncogenic signaling pathways in multiple tumor types is the unique isomerase Pin1. However, available Pin1 inhibitors lack the required specificity and potency. Using mechanism-based screening, here we find that all-trans retinoic acid (ATRA)--a therapy for acute promyelocytic leukemia (APL) that is considered the first example of targeted therapy in cancer, but its drug target remains elusive--inhibits and degrades active Pin1 selectively in cancer cells by directly binding to the substrate phosphate- and proline-binding pockets in the Pin1 active site. ATRA-induced Pin1 ablation degrades the fusion oncogene PML-RARα and treats APL in cell and animal models and human patients. ATRA-induced Pin1 ablation also inhibits triple negative breast cancer cell growth in human cells and in animal models by acting on many Pin1 substrate oncogenes and tumor suppressors. Thus, ATRA simultaneously blocks multiple Pin1-regulated cancer-driving pathways, an attractive property for treating aggressive and drug-resistant tumors

XRF derived elemental ratios and carbon content from ODP Site 177-722

Data included in this entry was sampled from ODP Site 722 (16.6218°N/59.7953°E). Original drilling was carried out by E/V JOIDES Resolution as part of ODP leg 117 between 6th and 8th of September 1987. The samples included in this entry were all cored originally by XCB. Sampling was carried out in Kochi core repository in 2018

Updated age model for ODP Site 177-722

Data included in this entry was sampled from ODP Site 722 (16.6218°N/59.7953°E). Original drilling was carried out by E/V JOIDES Resolution as part of ODP leg 117 between 6th and 8th of September 1987. The samples included in this entry were all cored originally by XCB. Sampling was carried out in Kochi core repository in 2018

Organic matter derived stable isotopes from ODP Site 177-722

Data included in this entry was sampled from ODP Site 722 (16.6218°N/59.7953°E). Original drilling was carried out by E/V JOIDES Resolution as part of ODP leg 117 between 6th and 8th of September 1987. The samples included in this entry were all cored originally by XCB. Sampling was carried out in Kochi core repository in 2018