Identification of a Taraxacum brevicorniculatum rubber elongation factor protein that is localized on rubber particles and promotes rubber biosynthesis

Two protein families required for rubber biosynthesis in Taraxacum brevicorniculatum have recently been characterized, namely the cis‐prenyltransferases (TbCPTs) and the small rubber particle proteins (TbSRPPs). The latter were shown to be the most abundant proteins on rubber particles, where rubber biosynthesis takes place. Here we identified a protein designated T. brevicorniculatum rubber elongation factor (TbREF) by using mass spectrometry to analyze rubber particle proteins. TbREF is homologous to the TbSRPPs but has a molecular mass that is atypical for the family. The promoter was shown to be active in laticifers, and the protein itself was localized on the rubber particle surface. In TbREF‐silenced plants generated by RNA interference, the rubber content was significantly reduced, correlating with lower TbCPT protein levels and less TbCPT activity in the latex. However, the molecular mass of the rubber was not affected by TbREF silencing. The colloidal stability of rubber particles isolated from TbREF‐silenced plants was also unchanged. This was not surprising because TbREF depletion did not affect the abundance of TbSRPPs, which are required for rubber particle stability. Our findings suggest that TbREF is an important component of the rubber biosynthesis machinery in T. brevicorniculatum, and may play a role in rubber particle biogenesis and influence rubber production.     

Navigating the complexity of ecological stability

Human actions challenge nature in many ways. Ecological responses are ineluctably complex, demanding measures that describe them succinctly. Collectively, these measures encapsulate the overall ‘stability’ of the system. Many international bodies, including the Intergovernmental Science‐Policy Platform on Biodiversity and Ecosystem Services, broadly aspire to maintain or enhance ecological stability. Such bodies frequently use terms pertaining to stability that lack clear definition. Consequently, we cannot measure them and so they disconnect from a large body of theoretical and empirical understanding. We assess the scientific and policy literature and show that this disconnect is one consequence of an inconsistent and one‐dimensional approach that ecologists have taken to both disturbances and stability. This has led to confused communication of the nature of stability and the level of our insight into it. Disturbances and stability are multidimensional. Our understanding of them is not. We have a remarkably poor understanding of the impacts on stability of the characteristics that define many, perhaps all, of the most important elements of global change. We provide recommendations for theoreticians, empiricists and policymakers on how to better integrate the multidimensional nature of ecological stability into their research, policies and actions.     

Characterization of novel nonacid glycosphingolipids as biomarkers of human gastric adenocarcinoma

Changes in glycosphingolipid structures have been shown to occur during the development of several types of human cancers, generating cancer-specific carbohydrate structures that could be used as biomarkers for diagnosis and therapeutic targeting. In this study, we characterized nonacid glycosphingolipids isolated from a human gastric adenocarcinoma by mass spectrometry, enzymatic hydrolysis, and by binding with a battery of carbohydrate-recognizing ligands. We show that the majority of the complex nonacid glycosphingolipids had type 2 (Galβ4GlcNAc) core chains (neolactotetraosylceramide, the Le^x, H type 2, x₂, and the P1 pentaosylceramides, and the Le^y, A type 2, and neolacto hexaosylceramides). We also found glycosphingolipids with type 1 (Galβ3GlcNAc) core (lactotetraosylceramide and the H type 1 pentaosylceramide) and globo (GalαGal) core chains (globotriaosylceramide and globotetraosylceramide). Interestingly, we characterized two complex glycosphingolipids as a P1 heptaosylceramide (Galα4Galβ4GlcNAcβ3Galβ4GlcNAcβ3Gal β4Glcβ1Cer) and a branched P1 decaosylceramide (Galα4Gal β4GlcNAcβ3(Galα4Galβ4GlcNAcβ6)Galβ4GlcNAcβ3Galβ4Glc β1Cer). These are novel glycosphingolipid structures and the first reported cases of complex glycosphingolipids larger than pentaosylceramide carrying the P1 trisaccharide. We propose that these P1 glycosphingolipids may represent potential biomarkers for the early diagnosis of gastric cancer.     

Environmental filtering and taxonomic relatedness underlie the species richness–evenness relationship

We examined the relationship between species richness (S) and evenness (J) within a novel, community assembly framework. We hypothesized that environmental stress leads to filtering (increasing the proportional abundance of tolerant species) and taxonomic dispersion (decreasing the number of species within genera and families). Environmental filtering would cause a decline in S by eliminating some stress-sensitive species and a reduction of J by allowing only tolerant species to maintain large populations. Taxonomic relatedness may influence both S and J by controlling the nature of interspecific interactions—positive under taxonomic dispersion versus negative under taxonomic clustering. Therefore, the S–J relationship may be a product of environmental filtering and taxonomic relatedness. We tested this framework with redundancy analyses and structural equation models using continental stream diatom and fish data. We confirmed that (i) environmental stress, defined by watershed forest cover, slope, and temperature, caused filtering (lower sensitive:tolerant species abundance ratios) and taxonomic dispersion (elevated genus:species richness and family:species richness ratios); (ii) S and J, which declined with filtering and taxonomic dispersion, exhibited a positive relationship; and (iii) the role of filtering on J was pronounced only under stressful conditions, while taxonomic dispersion remained an important predictor of J across stressful and favorable environments.     

Prey diversity effects on ecosystem functioning depend on consumer identity and prey composition

For migratory species, acquisition and allocation of energy after arrival on the breeding grounds largely determine reproductive decisions. Few studies have investigated underlying physiological mechanisms driving variation in breeding phenology so far. We linked physiological state to individual timing of breeding in pre-laying arctic-nesting female peregrine falcons (Falco peregrinus tundrius). We captured females from two populations 2–20 days before egg-laying to assess plasma concentration of β-hydroxybutyric acid (BUTY) and triglyceride (TRIG), two metabolites known to reflect short-term changes in fasting and fattening rate, respectively. We also assessed baseline corticosterone (CORTb), a hormone that mediates energy allocation, and the scaled mass index (SMI) as an indicator of somatic body reserves. Plasma BUTY was slightly higher during the pre-recruiting period compared to the period of rapid follicular growth, indicating a reduction in catabolism of lipid reserves before investment in follicle development. Conversely, TRIG levels increased in pre-recruiting females, and best-predicted individual variation in pre-laying interval and lay date. A marked increase in CORTb occurred concomitantly with the onset of rapid follicle growth. SMI was highly variable possibly reflecting variation in food availability or individuals at different stages. Results suggest that (1) lower rates of pre-laying fattening and/or lower mobilization rate of lipoproteins to ovarian follicles delayed laying, and (2) an elevation in pre-laying CORTb may result from, or be required to compensate for, the energetic costs of egg production. Results of this study illustrate how variation in the allocation of energy before laying can influence individual fitness-related reproductive decisions.     

An essential role of the autophagy activating kinase ULK1 in snRNP biogenesis

The biogenesis of small uridine-rich nuclear ribonucleoproteins (UsnRNPs) depends on the methylation of Sm proteins catalyzed by the methylosome and the subsequent action of the SMN complex, which assembles the heptameric Sm protein ring onto small nuclear RNAs (snRNAs). In this sophisticated process, the methylosome subunit pICln (chloride conductance regulatory protein) is attributed to an exceptional key position as an ‘assembly chaperone’ by building up a stable precursor Sm protein ring structure. Here, we show that—apart from its autophagic role—the Ser/Thr kinase ULK1 (Uncoordinated [unc-51] Like Kinase 1) functions as a novel key regulator in UsnRNP biogenesis by phosphorylation of the C-terminus of pICln. As a consequence, phosphorylated pICln is no longer capable to hold up the precursor Sm ring structure. Consequently, inhibition of ULK1 results in a reduction of efficient UsnRNP core assembly. Thus ULK1, depending on its complex formation, exerts different functions in autophagy or snRNP biosynthesis.     

Comparative chemical analysis of body odor in great apes

Olfaction is important across the animal kingdom for transferring information on, for example, species, sex, group membership, or reproductive parameters. Its relevance has been established in primates including humans, yet research on great apes still is fragmentary. Observational evidence indicates that great apes use their sense of smell in various contexts, but the information content of their body odor has not been analyzed. Our aim was therefore to compare the chemical composition of body odor in great ape species, namely Sumatran orangutans (Pongo abelii (Lesson, 1827), one adult male, five adult females, four nonadults), Western lowland gorillas (Gorilla gorilla gorilla (Savage, 1847), one adult male, two adult females, one nonadult), common chimpanzees (Pan troglodytes (Blumenbach, 1775), four adult males, nine adult females, four nonadults), and bonobos (Pan paniscus (Schwarz, 1929), two adult males, four adult females, two nonadults). We collected 195 samples (five per individual) of 39 captive individuals using cotton swabs and analyzed them using gas chromatography mass spectrometry. We compared the sample richness and intensity, similarity of chemical composition, and relative abundance of compounds. Results show that species, age, and potentially sex have an impact on the variance between odor profiles. Richness and intensity varied significantly between species (gorillas having the highest, bonobos the lowest richness and intensity), and with age (both increasing with age). Richness and intensity did not vary between sexes. Odor samples of the same species were more similar to each other than samples of different species. Among all compounds identified some were associated with age (N = 7), sex (N = 6), and species‐related (N = 37) variance. Our study contributes to the basic understanding of olfactory communication in hominids by showing that the chemical composition of body odor varies across species and individuals, containing potentially important information for social communication.     

Identification of phospholipase C gamma1 as a protein tyrosine phosphatase mu substrate that regulates cell migration

The receptor protein tyrosine phosphatase PTPµ has a cell‐adhesion molecule‐like extracellular segment and a catalytically active intracellular segment. This structure gives PTPµ the ability to transduce signals in response to cell–cell adhesion. Full‐length PTPµ is down‐regulated in glioma cells by proteolysis which is linked to increased migration of these cells in the brain. To gain insight into the substrates PTPµ may be dephosphorylating to suppress glioma cell migration, we used a substrate trapping method to identify PTPµ substrates in tumor cell lines. We identified both PKCδ and PLCγ1 as PTPµ substrates. As PLCγ1 activation is linked to increased invasion of cancer cells, we set out to determine whether PTPµ may be upstream of PLCγ1 in regulating glioma cell migration. We conducted brain slice assays using U87‐MG human glioma cells in which PTPµ expression was reduced by shRNA to induce migration. Treatment of the same cells with PTPµ shRNA and a PLCγ1 inhibitor prevented migration of the cells within the brain slice. These data suggest that PLCγ1 is downstream of PTPµ and that dephosphorylation of PLCγ1 is likely to be a major pathway through which PTPµ suppresses glioma cell migration. J. Cell. Biochem. 112: 39–48, 2011. © 2010 Wiley‐Liss, Inc.