Physiological and Molecular Background of Maize Cold-Tolerance Enhancement with S-methylmethionine Salicylate

Low temperature is amongst the most influential abiotic stress factors, having deep impact on plant growth, yield and productivity. Studies on beneficial effects of certain biologically active substances, S-methylmethionine (SMM) and salicylic acid (SA) have provided a lot of valuable information regarding their role to counteract harmful effects of environmental stresses such as chilling. To obtain a more complex and stable defence compound with an extended range of stress-protective effect, the new derivative S-methylmethionine salicylate (MMS) was synthesised from the natural, biologically active substances SMM and SA. Since both original materials have complex stress-protective roles, the new compound was expected to combine the effects of original substances and to stabilise the unstable SMM in the new compound, thus providing an extended stress tolerance. Photosynthetic efficiency and accumulation of stress-related metabolites (polyamines and flavonoids) were measured in chilled and control plants, with and without MMS pretreatment, and expression changes of several genes involved in the cold stress response were analysed by quantitative real-time PCR (RT-qPCR) and a detailed microarray study. Our data show how the MMS combines the effect of SMM and SA on molecular level, causing numerous changes in the gene expression pattern and metabolite content. MMS gives rise to a better physiological condition, thus it could provide an alternative, environmental friendly way to enhance the plants defence mechanisms against stressors. As MMS is more stable than SMM, it promises easier, more long-lasting and more cost-effective usage in agriculture, with a complementing effect of SA.

     

Differential effects of temperature change and human impact on European Late Quaternary mammalian extinctions

Species that inhabited Europe during the Late Quaternary were impacted by temperature changes and early humans, resulting in the disappearance of half of the European large mammals. However, quantifying the relative importance that each factor had in the extinction risk of species has been challenging, mostly due to the spatio‐temporal biases of fossil records, which complicate the calibration of realistic and accurate ecological niche modeling. Here, we overcome this problem by using ecotypes, and not real species, to run our models. We created 40 ecotypes with different temperature requirements (mean temperature from ?20 °C to 25 °C and temperature range from 10 °C to 40 °C) and used them to quantify the effect of climate change and human impact. Our results show that cold‐adapted ecotypes would have been highly affected by past temperature changes in Europe, whereas temperate and warm‐adapted ecotypes would have been positively affected by temperature change. Human impact affected all ecotypes negatively, and temperate ecotypes suffered the greatest impacts. Based on these results, the extinction of cold‐adapted species like Mammuthus primigenius may be related to temperature change, while the extinction of temperate species, like Crocuta crocuta, may be related to human impact. Our results suggest that temperature change and human impact affected different ecotypes in distinct ways, and that the interaction of both impacts may have shaped species extinctions in Europe.     

Changes of external respiration, brain circulation and the EEG in acute hypoxia in the subjects with different hypoxic resistance

Two groups of individuals were distinguished in experiments with acute hypoxic action (respiration of oxygen-nitrogen mixture with 8 % oxygen content) - with low (LHR) and high (HHR) resistance to hypoxia. In subjects of the LR group, slowing down of the pulse rate and lowering of arterial pressure in the shoulder artery were observed on the 5th-10th minute of hypoxia. In the HHR subjects, primary growth of the pulse rate was followed by its stabilization; no significant changes of the arterial pressure were observed. In LHR subjects, in the first 5-10 min of the hypoxia, a significantly lower level of the blood oxygen saturation was observed in comparison to the HHR. In the LHR group, there was a higher increment of amplitude-frequency index of the rheoencephalogram in comparison to the HHR, indicating a higher increment of the cerebral blood flow. The slowing down of the pulse rate in the LHR subjects was accompanied with increasing cerebral pulse volume, so that in spite of the pulse rate slowing, the minute volume of cerebral circulation increased. In the LHR subjects, two-phased dynamics of the EEG was observed: in the first phase there was a slow growth of theta- and delta-band EEG spectral power, in the second phase (on the 5th-10th min of hypoxia), sharp (200-300 % of the background level) growth of the EEG spectral power in those bands was observed. In the HHR subjects, gradual growth of EEG spectral power occurred with relative stabilization on the 10th-12th min of hypoxia. Possible role of the stress in the collapse-like reaction during acute hypoxia is analysed, which might cause increase of the oxygen request of the brain, higher growth of cerebral blood flow and more pronounced lowering of functional activity of the brain in the LHR subjects.     

Rosuvastatin beneficially alters the glomerular structure of kidneys from spontaneously hypertensive rats (SHRs)

The incidence of chronic renal diseases is increasing worldwide, and there is a great need to identify therapies capable of arresting or reducing disease progression. The current treatment of chronic nephropathies is limited to angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, but increasing clinical and experimental evidence suggests that statins could play a therapeutic role. Ultrastructural studies have shown the presence of gap junctions within all the cells of the glomerulus and podocytes have been found to contain primarily connexin-43. The present study aims to observe the beneficial effects of rosuvastatin on structural and ultrastructural renal morphology and on glomerular connexin-43 expression in normotensive rats and spontaneously hypertensive rats (SHR). Rats were randomly allocated into four groups: WKY-C: normotensive animals no receiving rosuvastatin; WKY-ROS: normotensive animals receiving rosuvastatin; SHR-C: hypertensive animals no receiving rosuvastatin; SHR-ROS: hypertensive animals receiving rosuvastatin. Our results show no differences in blood urea, creatinine, uric acid and creatine phosphokinase levels between the groups, however, there was an decreasing of 24-h protein excretion in SHR-ROS. Capsular area in SHR-ROS was decreased, however, there was no alteration in urinary space. By transmission electron microscopy the slit diaphragm and podocyte foot processes were more preserved in SHR-ROS. By scanning electron microscopy the podocyte foot processes were more preserved in SHR-ROS. Increased connexin-43 immunofluorescence was observed in glomeruli of WKY-ROS and SHR-ROS. In conclusion, we hypothesize that renal pleiotropic effect of rosuvastatin can be a therapeutic tool for improving kidney ultrastructure and, consequently, renal function in hypertensive individuals.     

Essential oils from neotropical Myrtaceae: chemical diversity and biological properties

Myrtaceae family (121 genera, 3800-5800 spp.) is one of the most important families in tropical forests. They are aromatic trees or shrubs, which frequently produce edible fruits. In the neotropics, ca. 1000 species were found. Several members of this family are used in folk medicine, mainly as an antidiarrheal, antimicrobial, antioxidant, cleanser, antirheumatic, and anti-inflammatory agent and to decrease the blood cholesterol. In addition, some fruits are eaten fresh or used to make juices, liqueurs, and sweets very much appreciated by people. The flavor composition of some fruits belonging to the Myrtaceae family has been extensively studied due to their pleasant and intense aromas. Most of the essential oils of neotropical Myrtaceae analyzed so far are characterized by predominance of sesquiterpenes, some with important biological properties. In the present work, chemical and pharmacological studies carried out on neotropical Myrtaceae species are reviewed, based on original articles published since 1980. The uses in folk medicine and chemotaxonomic importance of secondary metabolites are also briefly discussed.     

Disentangling the relative importance of climate,size and competition on tree growth in Iberian forests: implications for forest management under global change

Most large‐scale multispecies studies of tree growth have been conducted in tropical and cool temperate forests, whereas Mediterranean water‐limited ecosystems have received much less attention. This limits our understanding of how growth of coexisting tree species varies along environmental gradients in these forests, and the implications for species interactions and community assembly under current and future climatic conditions. Here, we quantify the absolute effect and relative importance of climate, tree size and competition as determinants of tree growth patterns in Iberian forests, and explore interspecific differences in the two components of competitive ability (competitive response and effect) along climatic and size gradients. Spatially explicit neighborhood models were developed to predict tree growth for the 15 most abundant Iberian tree species using permanent‐plot data from the Spanish Second and Third National Forest Inventory (IFN). Our neighborhood analyses showed a climatic and size effect on tree growth, but also revealed that competition from neighbors has a comparatively much larger impact on growth in Iberian forests. Moreover, the sensitivity to competition (i.e. competitive response) of target trees varied markedly along climatic gradients causing significant rank reversals in species performance, particularly under xeric conditions. We also found compelling evidence for strong species‐specific competitive effects in these forests. Altogether, these results constitute critical new information which not only furthers our understanding of important theoretical questions about the assembly of Mediterranean forests, but will also be of help in developing new guidelines for adapting forests in this climatic boundary to global change. If we consider the climatic gradients of this study as a surrogate for future climatic conditions, then we should expect absolute growth rates to decrease and sensitivity to competition to increase in most forests of the Iberian Peninsula (in all but the northern Atlantic forests), making these management considerations even more important in the future.     

Future climate‐driven shifts in distribution of Calanus finmarchicus

Calanus finmarchicus is a key‐structural species of the North Atlantic polar biome. The species plays an important trophic role in subpolar and polar ecosystems as a grazer of phytoplankton and as a prey for higher trophic levels such as the larval stages of many fish species. Here, we used a recently developed ecological niche model to assess the ecological niche (sensu Hutchinson) of C. finmarchicus and characterize its spatial distribution. This model explained about 65% of the total variance of the observed spatial distribution inferred from an independent dataset (data of the continuous plankton recorder survey). Comparisons with other types of models (structured population and ecophysiological models) revealed a clear similarity between modeled spatial distributions at the scale of the North Atlantic. Contemporary models coupled with future projections indicated a progressive reduction of the spatial habitat of the species at the southern edge and a more pronounced one in the Georges Bank, the Scotian Shelf and the North Sea and a potential increase in abundance at the northern edge of its spatial distribution, especially in the Barents Sea. These major changes will probably lead to a major alteration of the trophodynamics of North Atlantic ecosystems affecting the trophodynamics and the biological carbon pump.