Is the oceanic heat flux on the central Amundsen sea shelf caused by barotropic or baroclinic currents?

Kalen, O.,Assmann, K.M.,Wahlin, A.K.,Ha, H.K.,Kim, T.W.,Lee, S.H. Pergamon Press 2016 Deep-sea research. Part II, Topical studies in oce Vol.123 No.-

The glaciers that drain the West Antarctic Ice Sheet into the Amundsen Sea are accelerating and experiencing increased basal melt of the floating ice shelves. Warm and salty deep water has been observed to flow southward in deep troughs leading from the shelf break to the inner shelf area where the glaciers terminate. It has been suggested that the melting induced by this warm water is responsible for the acceleration of the glaciers. Here we investigate the structure of the currents and the associated heat flow on the shelf using in-situ observations from 2008 to 2014 in Dotson Trough, the main channel in the western part of the Amundsen Sea shelf, together with output from a numerical model. The model is generally able to reproduce the observed velocities and temperatures in the trough, albeit with a thicker warm bottom layer. In the absence of measurements of sea surface height we define the barotropic component of the flow as the vertical average of the velocity. It is shown that the flow is dominated by warm barotropic inflows on the eastern side and colder and fresher barotropic outflows on the western side. The transport of heat appears to be primarily induced by this clockwise barotropic circulation in the trough, contrary to earlier studies emphasizing a bottom-intensified baroclinic inflow as the main contributor.

Ca²⁺-dependent GTPase, Extra-large G Protein 2 (XLG2), Promotes Activation of DNA-binding Protein Related to Vernalization 1 (RTV1), Leading to Activation of Floral Integrator Genes and Early Flowering in<i>Arabidopsis</i>

Heo, Jae Bok,Sung, Sibum,Assmann, Sarah M. American Society for Biochemistry and Molecular Bi 2012 The Journal of biological chemistry Vol.287 No.11

Potato RNA-binding Proteins StUBA2a/b and StUBA2c Induces Early Leaf Senescence

Jong-Kuk Na,Sarah M Assmann 한국원예학회 2016 한국원예학회 학술발표요지 Vol.2016 No.10

Expression of potato RNA-binding proteins StUBA2a/b and StUBA2c induces hypersensitive-like cell death and early leaf senescence in <i>Arabidopsis</i>

Na, Jong-Kuk,Kim, Jae-Kwang,Kim, Dool-Yi,Assmann, Sarah M. Oxford University Press 2015 Journal of experimental botany Vol.66 No.13

<P>The <I>Arabidopsis thaliana</I> genome encodes three RNA-binding proteins (RBPs), UBP1-associated protein 2a (UBA2a), UBA2b, and UBA2c, that contain two RNA-recognition motif (RRM) domains. They play important roles in wounding response and leaf senescence, and are homologs of <I>Vicia faba</I> abscisic-acid-activated protein kinase-interacting protein 1 (VfAKIP1). The potato (<I>Solanum tuberosum</I>) genome encodes at least seven AKIP1-like RBPs. Here, two potato RBPs have been characterized, StUBA2a/b and StUBA2c, that are homologous to VfAKIP1 and <I>Arabidopsis</I> UBA2s. Transient expression of <I>StUBA2</I>s induced a hypersensitive-like cell death phenotype in tobacco leaves, and an RRM-domain deletion assay of StUBA2s revealed that the first RRM domain is crucial for the phenotype. Unlike overexpression of <I>Arabidopsis UBA2</I>s, constitutive expression of <I>StUBA2a/b</I> in <I>Arabidopsis</I> did not cause growth arrest and lethality at the young seedling stage, but induced early leaf senescence. This phenotype was associated with increased expression of defence- and senescence-associated genes, including pathogen-related genes (<I>PR</I>) and a senescence-associated gene (<I>SAG13</I>), and it was aggravated upon flowering and ultimately resulted in a shortened life cycle. Leaf senescence of <I>StUBA2a/b Arabidopsis</I> plants was enhanced under darkness and was accompanied by H<SUB>2</SUB>O<SUB>2</SUB> accumulation and altered expression of autophagy-associated genes, which likely cause cellular damage and are proximate causes of the early leaf senescence. Expression of salicylic acid signalling and biosynthetic genes was also upregulated in <I>StUBA2a/b</I> plants. Consistent with the localization of UBA2s-GFPs and VfAKIP1-GFP, soluble-modified GFP-StUBA2s localized in the nucleus within nuclear speckles. StUBA2s potentially can be considered for transgenic approaches to induce potato shoot senescence, which is desirable at harvest.</P>

PDR-type ABC transporter mediates cellular uptake of the phytohormone abscisic acid

Kang, Joohyun,Hwang, Jae-Ung,Lee, Miyoung,Kim, Yu-Young,Assmann, Sarah M.,Martinoia, Enrico,Lee, Youngsook Proceedings of the National Academy of Sciences 2010 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.107 No.5

<P>Abscisic acid (ABA) is a ubiquitous phytohormone involved in many developmental processes and stress responses of plants. ABA moves within the plant, and intracellular receptors for ABA have been recently identified; however, no ABA transporter has been described to date. Here, we report the identification of the ATP-binding cassette (ABC) transporter Arabidopsis thaliana Pleiotropic drug resistance transporter PDR12 (AtPDR12)/ABCG40 as a plasma membrane ABA uptake transporter. Uptake of ABA into yeast and BY2 cells expressing AtABCG40 was increased, whereas ABA uptake into protoplasts of <I>atabcg40</I> plants was decreased compared with control cells. In response to exogenous ABA, the up-regulation of ABA responsive genes was strongly delayed in <I>atabcg40</I> plants, indicating that ABCG40 is necessary for timely responses to ABA. Stomata of loss-of-function <I>atabcg40</I> mutants closed more slowly in response to ABA, resulting in reduced drought tolerance. Our results integrate ABA-dependent signaling and transport processes and open another avenue for the engineering of drought-tolerant plants.</P>

Subinertial Oscillations on the Amundsen Sea Shelf, Antarctica

Wå,hlin, A. K.,Kalé,n, O.,Assmann, K. M.,Darelius, E.,Ha, H. K.,Kim, T. W.,Lee, S. H. AMERICAN METEOROLOGICAL SOCIETY 2016 Journal of physical oceanography Vol.46 No.9

<P>Mooring data from the western flank of Dotson trough, Amundsen Sea shelf region, show the presence of barotropic oscillations with a period of 40-80 h. The oscillations are visible in velocity, temperature, salinity, and pressure and are comparable to tides in magnitude. The period of the oscillations corresponds to topographic Rossby waves of low group velocity and a wavelength of about 40 km, that is, the half-width of the channel. It is suggested that these resonant topographic Rossby waves cause the observed peak in the wave spectra. The observations show that sparseCTDdata from this region should be treated with caution and need to be complemented with moorings or yo-yo stations in order to give a representative picture for the hydrography.</P>

Tucumã (Astrocaryum aculeatum) Prevents Oxidative and DNA Damage to Retinal Pigment Epithelium Cells

Beatriz da Silva Rosa Bonadiman,Cláudia Chaves,Charles Elias Assmann,Grazielle Castagna Cezimbra Weis,Audrei de Oliveira Alves,Amanda Leitão Gindri,Cláudio Chaves,Ivana Beatrice Mânica da Cruz,Ariane 한국식품영양과학회 2021 Journal of medicinal food Vol.24 No.10

Eye diseases have a negative impact on the eyesight quality of the world population. The age-related macular degeneration (AMD) draws special attention since it is a chronic disorder characterized by oxidative and inflammatory damage to the retinal epithelial pigment, which triggers progressive vision loss. In the Brazilian Amazon, Astrocaryum aculeatum is an Amazonian fruit (Tucumã) used by riverside communities in traditional medicine to treat a number of ailments. These communities have recently shown to have increased longevity and reduced prevalence of age-related morbidity. Thus, the aim of this research was to chemically characterize and analyze the in vitro antioxidant effect and molecular damage prevention of the Tucumã ethanolic extract in retinal pigment epithelium (RPE) cells in a model for AMD. The extract was chemically characterized by ultra-high-performance liquid chromatography (HPLC) coupled with diode-array detection and mass spectrophotometry (HPLC-DAD-MS). In vitro protocols were performed, and the cytopreventive effect of Tucumã on RPE cells exposed to high concentrations of superoxide anion, an oxidant and genotoxic molecule, as well as the effect of Tucumã extract on oxidative and molecular makers were assessed. Biochemical and flow cytometry analyses were conducted in these protocols. The extract presents high concentrations of caffeic acid, gallic acid, catechin, luteolin, quercetin, and rutin. Treatment did not show cytotoxic effects in cells treated only with extract at 50 μg/mL. In fact, it improved cell viability and was able to prevent necrosis and apoptosis, and oxidative and molecular damage was significantly reduced. In summary, Tucumã is an important Amazon fruit, which seems to contribute significantly to improve human health conditions, as our findings suggest that its extract has a relevant chemical matrix rich in antioxidant molecules, and its consumption could improve eye health and contribute to prevention against oxidative stress through cytoprevention, reactive oxygen species reduction, and maintenance of DNA integrity in retinal pigment epithelium (RPE) cells.

Glider observations of the Dotson Ice Shelf outflow

Miles, T.,Lee, S.H.,Wahlin, A.,Ha, H.K.,Kim, T.W.,Assmann, K.M.,Schofield, O. Pergamon Press 2016 Deep-sea research. Part II, Topical studies in oce Vol.123 No.-

The Amundsen Sea is one of the most productive polynyas in the Antarctic per unit area and is undergoing rapid changes including a reduction in sea ice duration, thinning ice sheets, retreat of glaciers and the potential collapse of the Thwaites Glacier in Pine Island Bay. A growing body of research has indicated that these changes are altering the water mass properties and associated biogeochemistry within the polynya. Unfortunately difficulties in accessing the remote location have greatly limited the amount of in situ data that has been collected. In this study data from a Teledyne-Webb Slocum glider was used to supplement ship-based sampling along the Dotson Ice Shelf (DIS). This autonomous underwater vehicle revealed a detailed view of a meltwater laden outflow from below the western flank of the DIS. Circumpolar Deep Water intruding onto the shelf drives glacial melt and the supply of macronutrients that, along with ample light, supports the large phytoplankton blooms in the Amundsen Sea Polynya. Less well understood is the source of micronutrients, such as iron, necessary to support this bloom to the central polynya where chlorophyll concentrations are highest. This outflow region showed decreasing optical backscatter with proximity to the bed indicating that particulate matter was sourced from the overlying glacier rather than resuspended sediment. This result suggests that particulate iron, and potentially phytoplankton primary productivity, is intrinsically linked to the magnitude and duration of sub-glacial melt from Circumpolar Deep Water intrusions onto the shelf.