Biosystematics of the monocotyledoneae—flavonoid patterns in leaves of the liliaceae

In a leaf survey of 168 species of the Liliaceae, most of the major flavonoid classes were found to be represented in the family. Flavonols occurred most frequently: quercetin and kaempferol were detected in 40% and 42% of the sample respectively, while the flavones luteolin and apigenin were present in only 24% and 20% of the sample. Methylated derivatives, i.e. isorhamnetin, diosmetin and tricin were rare. Procyanidins were present in 17 species, flavonoid sulphates in only one species and flavone C-glycosides in only three species. Anthraquinone pigments were identified in species of Aloe Asphodeline and Asphodelus. Three new flavonoid glycosides were characterised during the course of the survey: diosmetin 7-diglucoside in Colchicum byzanthinum and tricin 7-fructosylglucoside and tricin 7-rutinoside-4′-glucoside in Hyacinthus orientalis cv. ‘Quean of the Pinks’. On the basis of the flavonoid survey, the subfamilies of the Liliaceae may be grouped into those containing flavonols only, those with flavones only or those having both flavonols and flavones. Members of the related families: Amaryllidaceae (17 species), Agavaceae (1 species) and Xanthorrhoeaceae (1 species) contained only flavonols. The subfamilies Scilloideae, Asphodeloideae and Melanthioideae show the most chemical variation whilst the Wurmbaeoideae and Lilioideae are the most homogeneous groups. The tribe Scilleae is unusual in that both flavone- and flavonol-containing genera occur and a wide variety of flavonoid types are represented. A comparison of the leaf flavonoids of the Liliaceae with those found in families related to the grasses showed that all except two classes of flavonoid compound (5-methylated flavones and 5-deoxyflavonoids) found in the Juncaceae. Cyperaceae, Palmae and Gramineae are present in the Liliaceae thus supporting the view that all four families could have arisen from Liliaceae-like ancestors.     

Can size distributions of European lake fish communities be predicted by trophic positions of their fish species?

An organism''s body size plays an important role in ecological interactions such as predator–prey relationships. As predators are typically larger than their prey, this often leads to a strong positive relationship between body size and trophic position in aquatic ecosystems. The distribution of body sizes in a community can thus be an indicator of the strengths of predator–prey interactions. The aim of this study was to gain more insight into the relationship between fish body size distribution and trophic position in a wide range of European lakes. We used quantile regression to examine the relationship between fish species'' trophic position and their log‐transformed maximum body mass for 48 fish species found in 235 European lakes. Subsequently, we examined whether the slopes of the continuous community size distributions, estimated by maximum likelihood, were predicted by trophic position, predator–prey mass ratio (PPMR), or abundance (number per unit effort) of fish communities in these lakes. We found a positive linear relationship between species'' maximum body mass and average trophic position in fishes only for the 75% quantile, contrasting our expectation that species'' trophic position systematically increases with maximum body mass for fish species in European lakes. Consequently, the size spectrum slope was not related to the average community trophic position, but there were negative effects of community PPMR and total fish abundance on the size spectrum slope. We conclude that predator–prey interactions likely do not contribute strongly to shaping community size distributions in these lakes.     

Plasmodium berghei leucine-rich repeat protein 1 downregulates protein phosphatase 1 activity and is required for efficient oocyst development

Protein phosphatase 1 (PP1) is a key enzyme for Plasmodium development. However, the detailed mechanisms underlying its regulation remain to be deciphered. Here, we report the functional characterization of the Plasmodium berghei leucine-rich repeat protein 1 (PbLRR1), an orthologue of SDS22, one of the most ancient and conserved PP1 interactors. Our study shows that PbLRR1 is expressed during intra-erythrocytic development of the parasite, and up to the zygote stage in mosquitoes. PbLRR1 can be found in complex with PbPP1 in both asexual and sexual stages and inhibits its phosphatase activity. Genetic analysis demonstrates that PbLRR1 depletion adversely affects the development of oocysts. PbLRR1 interactome analysis associated with phospho-proteomics studies identifies several novel putative PbLRR1/PbPP1 partners. Some of these partners have previously been characterized as essential for the parasite sexual development. Interestingly, and for the first time, Inhibitor 3 (I3), a well-known and direct interactant of Plasmodium PP1, was found to be drastically hypophosphorylated in PbLRR1-depleted parasites. These data, along with the detection of I3 with PP1 in the LRR1 interactome, strongly suggest that the phosphorylation status of PbI3 is under the control of the PP1–LRR1 complex and could contribute (in)directly to oocyst development. This study provides new insights into previously unrecognized PbPP1 fine regulation of Plasmodium oocyst development through its interaction with PbLRR1.     

Structures of nonsense-mediated mRNA decay factors UPF3B and UPF3A in complex with UPF2 reveal molecular basis for competitive binding and for neurodevelopmental disorder-causing mutation

UPF3 is a key nonsense-mediated mRNA decay (NMD) factor required for mRNA surveillance and eukaryotic gene expression regulation. UPF3 exists as two paralogs (A and B) which are differentially expressed depending on cell type and developmental stage and believed to regulate NMD activity based on cellular requirements. UPF3B mutations cause intellectual disability. The underlying molecular mechanisms remain elusive, as many of the mutations lie in the poorly characterized middle-domain of UPF3B. Here, we show that UPF3A and UPF3B share structural and functional homology to paraspeckle proteins comprising an RNA-recognition motif-like domain (RRM-L), a NONA/paraspeckle-like domain (NOPS-L), and extended α-helical domain. These domains are essential for RNA/ribosome-binding, RNA-induced oligomerization and UPF2 interaction. Structures of UPF2′s third middle-domain of eukaryotic initiation factor 4G (MIF4GIII) in complex with either UPF3B or UPF3A reveal unexpectedly intimate binding interfaces. UPF3B’s disease-causing mutation Y160D in the NOPS-L domain displaces Y160 from a hydrophobic cleft in UPF2 reducing the binding affinity ∼40-fold compared to wildtype. UPF3A, which is upregulated in patients with the UPF3B-Y160D mutation, binds UPF2 with ∼10-fold higher affinity than UPF3B reliant mainly on NOPS-L residues. Our characterization of RNA- and UPF2-binding by UPF3′s middle-domain elucidates its essential role in NMD.     

Thermal response in murine L929 cells lacking αB-crystallin expression and αB-crystallin expressing L929 transfectants

We investigated the role of B-crystallin expression in the development of thermotolerance in murine L929 cells. An initial heat-shock of 10 min at 45°C induced thermotolerance in these cells to a heat challenge at 45°C administered 24 h later. The thermotolerance ratio at 10^–1 isosurvival was 1.7. Expression of B-crystallin gene was not detected during the 24 h incubation at 37°C following heat shock by either northern or western blots. In contrast, inducible HSP70 synthesis was observed during this time period. Thus, this cell line provided an unique system in which to examine the effects of transfected B-crystallin on thermoresistance and thermotolerance. Cells stably transfected with B-crystallin under the control of an inducible promoter did not show a significant increase in the ability to develop thermotolerance. However, a stably transfected L929 clone expressing high levels of constitutive B-crystallin exhibited an approximately 50% increase in thermal resistance over parental and control cells. Though expression of B-crystallin is not requisite for the development of thermotolerance in L929 cells, overexpression of transfected B-crystallin can contribute to increased thermoresistance.     

The presence of glutathione and glutathione reductase in chloroplasts: A proposed role in ascorbic acid metabolism

Both glutathione and an NADPH-dependent glutathione reductase are present in spinach (Spinacia oleracea L.) chloroplasts. It is proposed that glutathione functions to stabilise enzymes of the Calvin cycle, and it may also act to keep ascorbic acid in chloroplasts in the reduced form.Abbreviations GSH tripeptide glutathione - GSH reduced form of glutathione - GSSG oxidised form of glutathione     

Secondary production and richness of native and non-native macroinvertebrates are driven by human-altered shoreline morphology in a large river

Animals living in extreme environments with predictable seasonality may have important life history events correlated to favourable periods. These animals pass critical life stages in protected habitats, especially during early life, often receiving parental care. It is thus hypothesized that juveniles rely on protective microhabitats provided by their parents, becoming independent only during favourable seasons. Semi-terrestrial crayfish Parastacus pugnax inhabit burrows in highly seasonal and predictable environments, thus being well suited to test this hypothesis. Following marked burrows and individual crayfish we examined the life history patterns of P. pugnax in their natural environment to test the predictions that (i) burrowing activity is higher during the wet season, (ii) reproductive events occur during favourable seasons and (iii) juveniles only disperse after reaching larger sizes. There was little or no burrowing activity during the dry season, when soil was more compact, but burrows became wider and had more openings during the wet season. After hatching, juveniles cohabited with adults for at least 4 months during the dry season. During this period juveniles grew considerably, starting independent lives during the wet season. These results suggest that the prolonged parent-offspring cohabitation evolved in response to the predictable seasonal variations in the crayfish habitat.