Effect of sodium channel abundance on Drosophila development, reproductive capacity and aging

The voltage-gated Na (+) channels (VGSC) are complex membrane proteins responsible for generation and propagation of the electrical signals through the brain, the skeletal muscle and the heart. The levels of sodium channels affect behavior and physical activity. This is illustrated by the maleless mutant allele (mle (napts)) in Drosophila, where the decreased levels of voltage-gated Na(+) channels cause temperature-sensitive paralysis. Here, we report that mle (napts) mutant flies exhibit developmental lethality, decreased fecundity and increased neurodegeneration. The negative effect of decreased levels of Na(+) channels on development and ts-paralysis was more pronounced at 18 and 29°C than at 25°C, suggesting particular sensitivity of the mle (napts) flies to temperatures above and below normal environmental conditions. Similarly, longevity of mle (napts) flies was unexpectedly short at 18 and 29°C compared with flies heterozygous for the mle (napts) mutation. Developmental lethality and neurodegeneration of mle (napts) flies was partially rescued by increasing the dosage of para, confirming a vital role of Na(+) channels in development, longevity and neurodegeneration of flies and their adaptation to temperatures.     

Senescence-induced ectopic expression of the A. tumefaciens ipt gene in wheat delays leaf senescence, increases cytokinin content, nitrate influx, and nitrate reductase activity, but does not affect grain yield

The manipulation of cytokinin levels by senescence-regulated expression of the Agrobacterium tumefaciens ipt gene through its control by the Arabidopsis SAG12 (senescence-associated gene 12) promoter is an efficient tool for the prolongation of leaf photosynthetic activity which potentially can affect plant productivity. In the present study, the efficiency of this approach was tested on wheat (Triticum aestivum L.)-a monocarpic plant characterized by a fast switch from vegetative to reproductive growth, and rapid translocation of metabolites from leaves to developing grains after anthesis. When compared with the wild-type (WT) control plants, the SAG12::ipt wheat plants exhibited delayed chlorophyll degradation only when grown under limited nitrogen (N) supply. Ten days after anthesis the content of chlorophyll and bioactive cytokinins of the first (flag) leaf of the transgenic plants was 32% and 65% higher, respectively, than that of the control. There was a progressive increase in nitrate influx and nitrate reductase activity. However, the SAG12::ipt and the WT plants did not show differences in yield-related parameters including number of grains and grain weight. These results suggest that the delay of leaf senescence in wheat also delays the translocation of metabolites from leaves to developing grains, as indicated by higher accumulation of ((15)N-labelled) N in spikes of control compared with transgenic plants prior to anthesis. This delay interferes with the wheat reproductive strategy that is based on a fast programmed translocation of metabolites from the senescing leaves to the reproductive sinks shortly after anthesis.     

Pleiotropic effects of the yeast Sal1 and Aac2 carriers on mitochondrial function via an activity distinct from adenine nucleotide transport

In Saccharomyces cerevisiae, SAL1 encodes a Ca2+ -binding mitochondrial carrier. Disruption of SAL1 is synthetically lethal with the loss of a specific function associated with the Aac2 isoform of the ATP/ADP translocase. This novel activity of Aac2 is defined as the V function (for Viability of aac2 sal1 double mutant), which is independent of the ATP/ADP exchange activity required for respiratory growth (the R function). We found that co-inactivation of SAL1 and AAC2 leads to defects in mitochondrial translation and mitochondrial DNA (mtDNA) maintenance. Additionally, sal1Delta exacerbates the respiratory deficiency and mtDNA instability of ggc1Delta, shy1Delta and mtg1Delta mutants, which are known to reduce mitochondrial protein synthesis or protein complex assembly. The V function is complemented by the human Short Ca2+ -binding Mitochondrial Carrier (SCaMC) protein, SCaMC-2, a putative ATP-Mg/Pi exchangers on the inner membrane. However, mitochondria lacking both Sal1p and Aac2p are not depleted of adenine nucleotides. The Aac2R252I and Aac2R253I variants mutated at the R252-254 triplet critical for nucleotide transport retain the V function. Likewise, Sal1p remains functionally active when the R479I and R481I mutations were introduced into the structurally equivalent R479-T480-R481 motif. Finally, we found that the naturally occurring V-R+ Aac1 isoform of adenine nucleotide translocase partially gains the V function at the expense of the R function by introducing the mutations P89L and A96 V. Thus, our data support the view that the V function is independent of adenine nucleotide transport associated with Sal1p and Aac2p and this evolutionarily conserved activity affects multiple processes in mitochondria.     

NADPH- and iron-dependent lipid peroxidation inhibit aromatase activity in human placental microsomes

During pregnancy placenta is the most significant source of lipid hydroperoxides and other reactive oxygen species (ROS). The increased production of lipid peroxides and other ROS is often linked to pre-eclampsia. It is already proved that placental endoplasmic reticulum may be an important place of lipid peroxides and superoxide radical production. In the present study we revealed that NADPH- and iron-dependent lipid peroxidation in human placental microsomes (HPM) inhibit placental aromatase--a key enzyme of estrogen biosynthesis in human placenta. We showed that significant inhibition of this enzyme is caused by small lipid peroxidation (TBARS (thiobarbituric acid-reactive substances)<4nmol/mg microsomal protein (m.p.)). More intensive lipid peroxidation (TBARS>9nmol/mg microsomal protein) diminishes aromatase activity to value being less than 5% of initial value. NADPH- and iron-dependent lipid peroxidation also causes disappearance of cytochrome P450 parallel to observed aromatase activity inhibition. EDTA, alpha-tocopherol, MgCl(2) and superoxide dismutase (SOD) prevent aromatase activity inhibition and cytochrome P450(AROM) degradation. Mannitol and catalase have not effect on TBARS synthesis, aromatase activity and cytochrome P450 degradation. In view of the above we postulate that the inhibition of aromatase activity observed is mainly a consequence of cytochrome P450(AROM) degradation induced by lipid radicals. The role of hydroxyl radical in cytochrome P450 degradation is negligible in our experimental conditions. The results presented here also suggest that the inhibition of aromatase activity can also take place in placenta at in vivo conditions.     

Facies variability in Lower Liassic carbonate successions of the Western Dinarides (Croatia)

Summary In the Western Dinarides the Lower Liassic carbonates are underlain by Upper Triassic “Hauptdolomit”, whereas the first appearance of the foraminiferOrbitopsella praecursor (Gümbel) marks the beginning of the Middle Liassic. Their composition, observed at several localities in Western Croatia, shows a correlation of sedimentation events, which took place during Early Liassic on the Adriatic-Dinaridic carbonate platform. Facies variability is interpreted as result of autocyclic sedimentary processes on which the carbonate platform reacted by periodical oscillations of sea-bottom near the fair-weather wavebase. As a consequence, the Lower Liassic carbonate successions in the Dinarides is characterized by stacking of two main types of coarsening-upward parasequences: (1) the basal part of the Lower Liassic succession is represented by parasequences composed of mudstones or pelletal-bioclastic wackestones as their lower members, and peloidal-bioclastic wackestone/packstones to grain-stones as their upper members; and (2) the upper part of the Lower Liassic succession with parasequences consisting of mudstones or pelletal-bioclastic wackestones overlain by ooid grainstones. Judging from the composition of parasequences and thickness relations of their members, the first type is interpreted to comprise late transgressive system tract (ITST) and/or early highstand system tract (eHST), while the second type corresponds to a late highstand system tract (1HST) and/or early lowstand system tract (eLST) of a third-order sequence.     

Invasive <Emphasis Type="Italic">Spiraea tomentosa</Emphasis>: a new host for monophagous <Emphasis Type="Italic">Earias clorana</Emphasis>?

The introduction of alien species can have a significant impact on the food preferences of native phytophagous insects. The moth Earias clorana L. has previously been considered to be monophagous, ingesting only plants in the genus Salix. In recent years, we have observed larval E. clorana feeding on Spiraea tomentosa L., an invasive shrub species in Central Europe that is native to North America. We hypothesised that this insect can feed on Spiraea tomentosa leaves with no negative effects on its growth and development, and that the leaves of Spiraea tomentosa as a source of food for E. clorana are equally as good as leaves of Salix viminalis L. Our results showed that despite significant differences in the chemical composition of the studied species’ leaves, including a much higher concentration of defence compounds (total soluble phenols and condensed tannins) in Spiraea tomentosa leaves than in those of Salix viminalis, feeding on a new host plant did not significantly affect the survival of larvae. The change in host plant had an unfavourable effect, however, on several parameters of growth and development for the larvae (masses of larvae and pupae, relative growth rates, and efficiency of conversion of ingested food). We conclude that, in comparison to Salix viminalis, Spiraea tomentosa is not a particularly favourable food for larval development. Perhaps, even without direct improvements in adult foraging efficiency, however, the costs of switching hosts may be minimised in larvae that develop on very abundant, invasive species, such as Spiraea tomentosa in Central Europe.