Populations ofLaminaria hyperborea at various latitudes

Summary 1. Populations ofLaminaria hyperborea were sampled in the Isle of Man (54° N), the Bergen area (60° N) in south-west Norway and the Tromsø area (70° N) in north Norway.2. The age of each plant was determined through the observation of a median section of the base of the stipe and the fresh weight of the stipe taken as a measure of the production of primary and secondary stipe tissue by the plant.3. At 4 m below mid-tide there was a slight difference in stipe weights at a given age between exposed and relatively sheltered sites in the Isle of Man. Differences between those in the Isle of Man and those at exposed sites near Bergen and near Tromsø were also slight. The longevity of the plants was greater near Bergen however.4. At 14 m below mid-tide plants were slightly smaller than at 4 m in the Isle of Man and a population from the same depth in a highly exposed site near Bergen had similar stipes. Again, however, the longevity was greater near Bergen, resulting in some very much larger plants.5. At 33 m below mid-tide near Bergen plants were very much smaller than at 14 m.6. Plants very small for their age were encountered in the Isle of Man only at the entrance to caves, where breaking waves seemed to cause damage.7. The largest plants for their age were found in shallow water rapids near Bergen. The longevity of these was low, however.8. It is concluded that local conditions have as much effect on early growth rate as latitude. Greater differences occur in the ability to become established and in longevity over the range of latitude studied and south-west Norway appears favourable for these.

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Populationen vonLaminaria hyperborea in verschiedenen geographischen Breiten

Kurzfassung Jahreszeitliche Wachstumsschwankungen beiLaminaria hyperborea prägen sich in der Anatomie des Stiels aus. Dadurch läßt sich das wahrscheinliche Alter einer Pflanze an einem Längsschnitt durch die Basis ihres Stiels bestimmen.L. hyperborea wächst im Sublitoral; vollständige Pflanzen kann man durch Tauchen erhalten. Die Art kommt an exponierten und halbexponierten Küsten Europas von 40° N bis 71° N vor, und zwar auf felsigem Untergrund oder festliegenden Blöcken von der Niedrigwasserlinie bis zu Tiefen von 4 bis 35 m. Je nach den örtlichen Gegebenheiten ist sie die dominierende Art, oder sie kommt vergesellschaftet mitL. digitata, L. saccharina, L. ochroleuca, Saccorhiza polyschides oderAlaria esculenta vor. Die untersuchten Pflanzen stammten aus Beständen von Standorten verschiedener geographischer Breite und abgestufter Exposition, hauptsächlich von der Isle of Man sowie von Süd- und Nordnorwegen. Gewicht und Länge des Stieles und der Lamina jeder Pflanze wurden gemessen und ihr wahrscheinliches Alter bestimmt. Am Ende der Periode des raschen Wachstums entspricht die Lamina einer Jahresproduktion; sie wird jährlich abgeworfen. Der Stiel dagegen ist mehrjährig und zeichnet den Wachstumsverlauf während der gesamten Lebensdauer einer Pflanze auf. Bei vergleichbarer Tiefe unter dem mittleren Meeresspiegel schwankt das Wachstum im allgemeinen an den untersuchten Standorten verschiedener geographischer Breite nicht mehr als unter den ökologischen Gegebenheiten eines Ortes. Jedoch pflegen an begünstigten Standorten der höheren Breiten die Pflanzen älter zu werden als bei Isle of Man. Bis zu einer Tiefe von 15 m nimmt das Wachstum nur wenig ab, in erheblich tieferem Wasser ist das Wachstum aber auffallend verringert. Die Pflanzen werden auch merklich kleiner, wenn sie am Eingang exponierter Höhlen wachsen. An Standorten, die ständig einer starken Strömung ausgesetzt sind, ist das Wachstum bei geringer Lebensdauer der Pflanzen intensiv.L. cucullata, vielleicht eine in ruhigem Wasser ausgebildete Form vonL. hyperborea, erzeugt ein im Verhältnis zum Stiel schwereres Laub.

     

Influences of light and UV-B on growth and sporulation of the green alga Ulva pertusa Kjellman

The cosmopolitan presence of Ulva spp. is partly due to its great reproductive ability, but relatively little information is available for the radiation conditions triggering reproduction. In the present study, we investigated the effect of photon irradiance, photoperiod, and spectral qualities of light on growth and reproduction of Ulva pertusa.During 8-day culture of discs cut from marginal parts of the thallus of U. pertusa, the size of the thallus discs was greatest at 10 μmol m⁻² s⁻¹, while saturation of reproduction occurred at 30 μmol m⁻² s⁻¹. The minimum photon irradiance allowing growth and reproduction was 5 and 10 μmol m⁻² s⁻¹, respectively. Rapid increases in the size and subsequent initiation of sporulation were observed in samples transferred to saturating irradiance from 5 μmol m⁻² s⁻¹ or darkness for 9 days. When exposed to different photoperiods (8:16-, 12:12-, 16:8-h LD and continuous light regimes) combined with different photon irradiances (10 and 100 μmol m⁻² s⁻¹), U. pertusa thallus showed that the thallus size attained at the low irradiance was similar in daylengths longer than 12 h per day, while the surface area increased in parallel with increasing light duration at the high irradiance. The degree of sporulation at 10 μmol m⁻² s⁻¹ varied, ranging from no sporulation in 8:16-h LD to 80% in 16:8-h LD and continuous light. On the other hand, there was no remarkable difference in the degree of sporulation between the photoperiods except for slightly smaller percentage sporulation in 8:16-h LD at 100 μmol m⁻² s⁻¹.At 5 μmol m⁻² s⁻¹, the growth of U. pertusa was markedly lower in green than in blue or red light, but there was no sporulation in any spectral quality. The degree of sporulation at 20 μmol m⁻² s⁻¹ was almost twice as much in blue or red as in green light.The size of plants irradiated with 1.0 W m⁻² of UV-B for 20-40 min increased by 18-21% relative to control, whereas higher UV irradiance caused inhibition of growth. There was a significantly lower incidence of sporulation in UV-B-irradiated plants with the degree of reduction being greater in those exposed to higher UV doses. The total biologically effective UV-B dose for 50% inhibition of sporulation was 0.085 Dose_eff kJ m⁻². The time required to achieve 50% inhibition would be longer than 13 h at depths below 1 m in Ahnin coastal waters. The vertical attenuation coefficient of PAR (λ=400-700 nm) and UV-B (λ=300-320 nm) in April 1998 at Ahnin on the eastern coast of Korea was 0.21 m⁻¹ for K_PAR and 0.54 m⁻¹ for K_UV-B. A large reduction of light quantity and rapid disappearance of blue wavelength occurred by shading from overlying thalli.Percentage inhibition of sporulation was only 14-18% at 150-200 μmol m⁻² s⁻¹ compared with 70% at 10 μmol m⁻² s⁻¹, when plants were incubated under different irradiances of PAR immediately after UV-B exposures.These different photoadaptive strategies for sporulation may in part account for the great ecological success of U. pertusa.     

Nitric oxide production occurs after cytosolic alkalinization during stomatal closure induced by abscisic acid

Abscisic acid (ABA) raised the cytosolic pH and nitric oxide (NO) levels in guard cells while inducing stomatal closure in epidermis of Pisum sativum. Butyrate (a weak acid) reduced the cytosolic pH/NO production and prevented stomatal closure by ABA. Methylamine (a weak base) enhanced the cytosolic alkalinization and aggravated stomatal closure by ABA. The rise in guard cell pH because of ABA became noticeable after 6 min and peaked at 12 min, while NO production started at 9 min and peaked at 18 min. These results suggested that NO production was downstream of the rise in cytosolic pH. The ABA-induced increase in NO of guard cells and stomatal closure was prevented by 2-phenyl-4,4,5,5-tetramethyl imidazoline-1-oxyl 3-oxide (cPTIO, a NO scavenger) and partially by N-nitro-L-Arg-methyl ester (L-NAME, an inhibitor of NO synthase). In contrast, cPTIO or L-NAME had only a marginal effect on the pH rise induced by ABA. Ethylene glycol tetraacetic acid (EGTA, a calcium chelator) prevented ABA-induced stomatal closure while restricting cytosolic pH rise and NO production. We suggest that during ABA-induced stomatal closure, a rise in cytosolic pH is necessary for NO production. Calcium may act upstream of cytosolic alkalinization and NO production, besides its known function as a downstream component.     

A pathway map of signaling events triggered upon SARS-CoV infection

Severe acute respiratory syndrome coronaviruses (SARS-CoVs) caused worldwide epidemics over the past few decades. Extensive studies on various strains of coronaviruses provided a basic understanding of the pathogenesis of the disease. Presently, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is leading a global pandemic with unprecedented challenges. This is the third coronavirus outbreak of this century. A signaling pathway map of signaling events induced by SARS-CoV infection is not yet available. In this study, we present a literature-annotated signaling pathway map of reactions induced by SARS-CoV infected cells. Multiple signaling modules were found to be orchestrated including PI3K-AKT, Ras-MAPK, JAK-STAT, Type 1 IFN and NFκB. The signaling pathway map of SARS-CoV consists of 110 molecules and 101 reactions mediated by SARS-CoV proteins. The pathway reaction data are available in various community standard data exchange formats including Systems Biology Graphical Notation (SBGN). The pathway map is publicly available through the GitHub repository and data in various formats can be freely downloadable.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12079-021-00642-2.     

Neurobiology: New connections between integrins and axon guidance

Axon guidance molecules such as netrins, semaphorins, Slits and ephrins provide the cues required for accurate patterning of axonal projections in the nervous system. Recent reports have described multiple paradigms by which these molecules interact with integrin adhesion receptors in and outside the neuronal tissues.     

Rac regulates phosphorylation of the myosin-II heavy chain, actinomyosin disassembly and cell spreading

GTPases of the Rho family regulate actinomyosin-based contraction in non-muscle cells. Activation of Rho increases contractility, leading to cell rounding and neurite retraction in neuronal cell lines. Activation of Rac promotes cell spreading and interferes with Rho-mediated cell rounding. Here we show that activation of Rac may antagonize Rho by regulating phosphorylation of the myosin-II heavy chain. Stimulation of PC12 cells or N1E-115 neuroblastoma cells with bradykinin induces phosphorylation of threonine residues in the myosin-II heavy chain; this phosphorylation is Ca2+ dependent and regulated by Rac. Both bradykinin-mediated and constitutive activation of Rac promote cell spreading, accompanied by a loss of cortical myosin II. Our results identify the myosin-II heavy chain as a new target of Rac-regulated kinase pathways, and implicate Rac as a Rho antagonist during myosin-II-dependent cell-shape changes.     

Engineering tolerance and hyperaccumulation of arsenic in plants by combining arsenate reductase and gamma-glutamylcysteine synthetase expression

We have developed a genetics-based phytoremediation strategy for arsenic in which the oxyanion arsenate is transported aboveground, reduced to arsenite, and sequestered in thiol-peptide complexes. The Escherichia coli arsC gene encodes arsenate reductase (ArsC), which catalyzes the glutathione (GSH)-coupled electrochemical reduction of arsenate to the more toxic arsenite. Arabidopsis thaliana plants transformed with the arsC gene expressed from a light-induced soybean rubisco promoter (SRS1p) strongly express ArsC protein in leaves, but not roots, and were consequently hypersensitive to arsenate. Arabidopsis plants expressing the E. coli gene encoding gamma-glutamylcysteine synthetase (gamma-ECS) from a strong constitutive actin promoter (ACT2p) were moderately tolerant to arsenic compared with wild type. However, plants expressing SRS1p/ArsC and ACT2p/gamma-ECS together showed substantially greater arsenic tolerance than gamma-ECS or wild-type plants. When grown on arsenic, these plants accumulated 4- to 17-fold greater fresh shoot weight and accumulated 2- to 3-fold more arsenic per gram of tissue than wild type or plants expressing gamma-ECS or ArsC alone. This arsenic remediation strategy should be applicable to a wide variety of plant species.     

Effects of starvation and desiccation on energy metabolism in desert and mesic Drosophila

Energy availability can limit the ability of organisms to survive under stressful conditions. In Drosophila, laboratory experiments have revealed that energy storage patterns differ between populations selected for desiccation and starvation. This suggests that flies may use different sources of energy when exposed to these stresses, but the actual substrates used have not been examined. We measured lipid, carbohydrate, and protein content in 16 Drosophila species from arid and mesic habitats. In five species, we measured the rate at which each substrate was metabolized under starvation or desiccation stress. Rates of lipid and protein metabolism were similar during starvation and desiccation, but carbohydrate metabolism was several-fold higher during desiccation. Thus, total energy consumption was lower in starved flies than desiccated ones. Cactophilic Drosophila did not have greater initial amounts of reserves than mesic species, but may have lower metabolic rates that contribute to stress resistance.