Abstract
Intraseasonal variation of rainfall extremes within boreal summer in the Indo-Pacific region is driven by the Boreal Summer Intraseasonal Oscillation (BSISO), a quasi-periodic north-eastward ...movement of convective precipitation from the Indian Ocean to the Western Pacific. Predicting the spatiotemporal location of the BSISO is essential for subseasonal prediction of rainfall extremes but still remains a major challenge due to insufficient understanding of its propagation pathway. Here, using unsupervised machine learning, we characterize how rainfall extremes travel within the region and reveal three distinct propagation modes: north-eastward, eastward-blocked, and quasi-stationary. We show that Pacific sea surface temperatures modulate BSISO propagation — with El Niño-like (La Niña-like) conditions favoring quasi-stationary (eastward-blocked) modes—by changing the background moist static energy via local overturning circulations. Finally, we demonstrate the potential for early warning of rainfall extremes in the region up to four weeks in advance.
The diversity of El Niño events is commonly described by two distinct flavors, the Eastern Pacific (EP) and Central Pacific (CP) type. While the remote impacts, that is, teleconnections, of EP and CP ...events have been studied for different regions individually, a global picture of their structure is still lacking. Here, we use Forman‐Ricci curvature applied on climate networks constructed from surface air temperature data to distinguish regional links from teleconnections. Our results confirm that both El Niño types influence the teleconnection patterns, however, with different spatial manifestations. Our analysis suggests that EP El Niños alter the general circulation which changes the teleconnection structure to primarily tropical teleconnections. In contrast, the teleconnection pattern of CP El Niños show only subtle changes to normal conditions. Moreover, this work identifies the dynamics of the Eastern Pacific as a proxy for the remote impact of both El Niño types.
Plain Language Summary
El Niño events, characterized by anomalous sea surface temperatures (SSTs) in the Tropical Pacific, come in two flavors; Eastern Pacific (EP) and Central Pacific (CP) types, depending on the longitudinal location of the strongest SST anomalies. Their remote impacts, known as teleconnections, differ. Although there are many studies investigating teleconnections of EP and CP events for individual target regions, a global analysis of the spatial distribution of their teleconnections is still lacking. In this study, we use the theory of complex networks to study EP and CP El Niño teleconnections. We construct “climate networks” from global surface air temperature data and use the notion of “curvature” of a network link to uncover their spatial organization. We show that the most negatively curved links highlight important teleconnection patterns that differ depending on the El Niño type. EP events change the teleconnection structure to the tropics while CP and Normal year conditions reveal teleconnections to all latitudes. Interestingly, the Central Pacific does not show many teleconnections, even during CP El Niño events which we attribute to the varying location of warm water anomalies in the Central Pacific. The Eastern Pacific changes more consistently allowing identifying remote impacts of both El Niños types.
Key Points
Ricci curvature of boreal winter climate networks reveals long‐range teleconnection structure
Eastern Pacific (EP) El Niños show primarily teleconnections in tropical while Central Pacific El Niños teleconnections on all latitudes
The EP contains robust teleconnections for both El Niño types
Small-angle X-ray and small-angle neutron scattering (SAXS/SANS) provide unique structural information on biomolecules and their complexes in solution. SANS may provide multiple independent data sets ...by means of contrast variation experiments, that is, by measuring at different D2O concentrations and different perdeuteration conditions of the biomolecular complex. However, even the combined data from multiple SAXS/SANS sets is by far insufficient to define all degrees of freedom of a complex, leading to a significant risk of overfitting when refining biomolecular structures against SAXS/SANS data. Hence, to control against overfitting, the low-information SAXS/SANS data must be complemented by accurate physical models, and, if possible, refined models should be cross-validated against independent data not used during the refinement. We present a method for refining atomic biomolecular structures against multiple sets of SAXS and SANS data using all-atom molecular dynamics simulations. Using the protein citrate synthase and the protein/RNA complex Sxl–Unr–msl2 mRNA as test cases, we demonstrate how multiple SAXS and SANS sets may be used for refinement and cross-validation, thereby excluding overfitting during refinement. For the Sxl–Unr–msl2 complex, we find that perdeuteration of the Unr domain leads to a unique, slightly compacted conformation, whereas other perdeuteration conditions lead to similar solution conformations compared to the nondeuterated state. In line with our previous method for predicting SAXS curves, SANS curves were predicted with explicit-solvent calculations, taking atomic models for both the hydration layer and the excluded solvent into account, thereby avoiding the use of solvent-related fitting parameters and solvent-reduced neutron scattering lengths. We expect the method to be useful for deriving and validating solution structures of biomolecules and soft-matter complexes, and for critically assessing whether multiple SAXS and SANS sets are mutually compatible.
Regulation of Plant Growth by Cytokinin Werner, Tomáš; Motyka, Václav; Strnad, Miroslav ...
Proceedings of the National Academy of Sciences - PNAS,
08/2001, Letnik:
98, Številka:
18
Journal Article
Recenzirano
Odprti dostop
Cytokinins are a class of plant-specific hormones that play a central role during the cell cycle and influence numerous developmental programs. Because of the lack of biosynthetic and signaling ...mutants, the regulatory roles of cytokinins are not well understood. We genetically engineered cytokinin oxidase expression in transgenic tobacco plants to reduce their endogenous cytokinin content. Cytokinin-deficient plants developed stunted shoots with smaller apical meristems. The plastochrone was prolonged, and leaf cell production was only 3-4% that of wild type, indicating an absolute requirement of cytokinins for leaf growth. In contrast, root meristems of transgenic plants were enlarged and gave rise to faster growing and more branched roots. These results suggest that cytokinins are an important regulatory factor of plant meristem activity and morphogenesis, with opposing roles in shoots and roots.
The genus Linum includes more than 230 globally distributed species, which have attracted great interest as they grow rapidly and are already sources of commercially important products, e.g. flax and ...linseed oil. Furthermore, they contain lignans such as podophyllotoxin (PTOX), deoxypodophyllotoxin (a precursor of both PTOX and 6-methoxypodophyllotoxin, the latter via β-peltatin, and β-peltatin-A-methyl ether) and various derivatives. Lignans are natural compounds derived from two 8,8′-linked C₆C₃ (propylbenzene) units. PTOX is an aryltetralin-lignan with strong cytotoxic and antiviral activities. Thus, it is used as a starting material for producing various semisynthetic derivatives that are widely used in chemotherapy, such as etoposide, teniposide and etopophos. It is currently produced largely from Podophyllum hexandrum and P. peltatum, slow-growing endangered species of the Berberidaceae. Hence, the possibility of producing it from Linum, especially members of section Syllinum under either in vitro or ex vitro conditions is highly attractive. This review summarizes related research, focusing on in vitro production of aryltetralin lignans from various Linum species and possible biotechnological strategies to improve their production. The key pathways, enzymes and genes involved are highlighted and future challenges that must be met to allow viable, large-scale production of this anticancer drug lead are discussed.
Key Message
Short-term exposure to high temperatures modulates the aromatic cytokinin profile of radiata pine embryonal masses when measured 8 weeks after initiation.
Recent research has demonstrated ...that cytokinins could be involved in abiotic stress responses. However, little research has been published about the role of endogenous aromatic cytokinins during these processes. Therefore, in this study, different temperature and incubation periods (23 ºC, 8 weeks; 40 ºC, 4 h; 50 ºC, 30 min; 60 ºC, 5 min) were applied during induction of radiata pine somatic embryogenesis and the aromatic cytokinin content of the resulting embryonal masses was measured. Results indicated that temperature during induction had a significant effect on the profile of most of the aromatic cytokinins detected. All tested higher temperatures than control provoked a decline in some free bases, including N
6
-benzyladenine,
ortho
-Topolin and
para
-Topolin. On the other hand, the values of N
6
-benzyladenine nucleotides, ribosides and irreversible metabolites (9G), as well as
para
-Topolin ribosides, increased in embryonal masses originating from 40 ºC treatment. These results suggest that despite not being traditionally considered part of the stress response machinery, aromatic cytokinins might be involved in heat-stress responses during early stages of somatic embryogenesis in radiata pine.
Immunogold electron microscopy (EM) study of Arabidopsis root apices analyzed using specific IAA antibody and high-pressure freeze fixation technique allowed, for the first time, vizualization of ...subcellular localization of IAA in cells assembled intactly within plant tissues. Our quantitative analysis reveals that there is considerable portion of IAA gold particles that clusters within vesicles and membraneous compartments in all root apex cells. There are clear tissue-specific and developmental differences of clustered IAA in root apices. These findings have significant consequences for our understanding of this small molecule which is controlling plant growth, development and behavior.
Endogenous gibberellins and brassinosteroids were quantified in 24 axenic microalgae strains from the Chlorophyceae, Trebouxiophyceae, Ulvophyceae and Charophyceae microalgae strains after 4 days in ...culture. This is the first report of endogenous gibberellins being successfully detected in microalgae. Between 18 and 20 gibberellins were quantified in all strains with concentrations ranging from 342.7 pg mg−1 DW in Raphidocelis subcapitata MACC 317–4746.1 pg mg−1 DW in Scotiellopsis terrestris MACC 44. Slower growing strains (S. terrestris MACC 44, Gyoerffyana humicola MACC 334, Nautococcus mamillatus MACC 716 and Chlorococcum ellipsoideum MACC 712) exhibited the highest gibberellin contents while lowest levels of gibberellins were found in faster growing strains (R. subcapitata MACC 317 and Coelastrum excentrica MACC 504). In all strains, the active gibberellin detected in the highest concentration was GA6, the predominant intermediates were GA15 and GA53 and the main biosynthetic end products were GA13 and GA51. Gibberellin profiles were similar in all strains except for the presence/absence of GA12 and GA12ald. To date this is the second report of endogenous brassinosteroids in microalgae. Brassinosteroids were detected in all 24 strains with concentrations ranging from 117.3 pg mg−1 DW in R. subcapitata MACC 317–977.8 pg mg−1 DW in Klebsormidium flaccidum MACC 692. Two brassinosteroids, brassinolide and castasterone were determined in all the strains. Generally, brassinolide occurred in higher concentrations than castasterone.
•Twenty four axenic microalgae strains were analyzed for their hormone content.•This is the first report of endogenous gibberellins in microalgae.•GA6 was the most abundant biologically active gibberellin.•This is the second report of endogenous brassinosteroids in microalgae.•Brassinolide and castasterone were detected in all 24 strains.
Antioxidant and antimicrobial activities as well as the quantity of phenolic substances (total phenol, flavonoid and phenolic acid contents) were determined in aqueous extracts of leaves, stems and ...flowers of Moltkia petraea (Tratt.) Griseb. from two mountainous localities (Sveti Jure and Sniježnica) in Croatia. In addition, the profile of phenolic acids was analyzed by UPLC–MS/MS. Antioxidant activities of all extracts in different test systems, namely the DPPH radical scavenging, reducing power assay and chelating activity, increased with extract concentration. Activity of the extracts from Sniježnica in β-carotene-linoleic acid assay did not differ from the activity of standard, BHA. The leaf extracts from Sniježnica demonstrated superior antioxidant activity in most of the assays, while the stem extract from the same locality was the most effective Fe2+ ion chelator. In general, the extracts from Sniježnica were more effective antioxidants than the corresponding extracts from Sveti Jure. The aqueous extracts of M. petraea did not show antimicrobial activity against bacteria and fungi tested in the diffusion and dilution assays.
How the application of commercial (thin film) flat panel display technology, used in the production of flexible displays and flexible digital X-ray detectors, can also be applied to reduce the ...manufacturing cost of wearable biomedical devices, as well as potentially improve their diagnostic functionality, is explored. As a technology platform to evaluate the presented new concept, a prototype photoplethysmograph biosensor using a flexible organic light-emitting diode display and pin photodiode (thin film) sensor technology for optical heart rate monitoring is developed.
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