Drought until death do us part: a case study of the desiccation-tolerance of a tropical moist forest seedling-tree,Licania platypus (Hemsl.) Fritsch

Studies of the desiccation tolerance of 15-month-old Licania platypus (Hemsl.) Fritsch seedlings were performed on potted plants. Pots were watered to field capacity and then dehydrated for 23-46 d to reach various visible wilting stages from slightly-wilted to dead. Root hydraulic conductance, k(r), was measured with a high-pressure flow meter and whole-stem hydraulic conductance, k(ws), was measured by a vacuum chamber method. Leaf punches were harvested for measurement of leaf water potential by a thermocouple psychrometer and for measurement of fresh- and dry-weight. L. platypus was surprisingly desiccation-tolerant, suggesting that most species of central Panama may be well adapted to the seasonality of rainfall in the region. The slightly-wilted stage corresponded to leaf water potentials and relative water contents of -2.7 MPa and 0.85, respectively, but plants did not die until these values fell to -7.5 MPa and 0.14, respectively. As desiccation proceeded k(r) and k(ws) declined relative to irrigated controls, but k(ws) was more sensitive to desiccation than k(r). Values of k(ws) declined by 70-85% in slightly-wilted to dead plants, respectively. By comparison, k(r) showed no significant change in slightly-wilted plants and fell by about 50% in plants having severely-wilted to dead shoots.     

Stathmin Is Dispensable for Tumor Onset in Mice

The microtubule-destabilizing protein stathmin is highly expressed in several types of tumor, thus deserving the name of oncoprotein 18. High levels of stathmin expression and/or activity favor the metastatic spreading and mark the most aggressive tumors, thus representing a realistic marker of poor prognosis. Stathmin is a downstream target of many signaling pathways, including Ras-MAPK, PI3K and p53, involved in both tumor onset and progression. We thus hypothesized that stathmin could also play a role during the early stages of tumorigenesis, an issue completely unexplored. In order to establish whether stathmin expression is necessary for tumor initiation, we challenged wild type (WT), stathmin heterozygous and stathmin knock-out (KO) mice with different carcinogens. Using well-defined mouse models of carcinogenesis of skin, bladder and muscle by the means of 7,12-dimethylbenz[α]antracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA), N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) and 3-methylcholanthrylene (3MC) treatments, respectively, we demonstrated that knock-out of stathmin has no impact on the onset of cancer in mice. No significant difference was noticed either when the Ras oncogene was mutated (skin carcinogenesis model) or when the p53 pathway was inactivated (bladder carcinomas and fibrosarcomas). Finally, we concomitantly impinged on p53 and Ras pathways, by generating WT and stathmin KO mouse embryo fibroblasts transformed with papilloma virus large T antigen (LgTAg) plus the K-Ras^G12V oncogene. In vivo growth of xenografts from these transformed fibroblasts did not highlight any significant difference depending on the presence or absence of stathmin. Overall, our work demonstrates that stathmin expression is dispensable for tumor onset, at least in mice, thus making stathmin a virtually exclusive marker of aggressive disease and a promising therapeutic target for advanced cancers.     

Activated alpha(2)-macroglobulin induces cell proliferation and mitogen-activated protein kinase activation by LRP-1 in the J774 macrophage-derived cell line

The low-density lipoprotein receptor-related protein-1 (LRP-1) is an endocytic receptor of activated forms of the proteinase inhibitor alpha(2)-macroglobulin (alpha(2)M*). It has been proposed that alpha(2)M* and LRP-1 modulate diverse cellular processes, including cell adhesion, proliferation, and migration, which are involved in inflammation and tumor progression. However, relatively little is known about the role of alpha(2)M*/LRP-1 interaction on these processes. In this work, we demonstrate that alpha(2)M* binding to LRP-1 induces cell proliferation and MAPK activation in the J774 macrophage-derived cell line, which were blocked by RAP, an antagonist of LRP-1-binding ligands, and by PD980059, a specific inhibitor for the Mek1-ERK1/2 pathway. In addition, we demonstrate that LPS, a bacterial product that it is known to down-regulate the LRP-1 expression on macrophage, abrogated the signaling activity triggered by alpha(2)M* on LPS-treated J774 cells. These results suggest that alpha(2)M*/LRP-1 interaction constitutes a key role in the macrophage functioning during inflammation and cancer.     

Evidence of a landlocked reproducing population of the marine pejerrey Odontesthes argentinensis (Actinopterygii; Atherinopsidae)

In South America, the order Atheriniformes includes the monophyletic genus Odontesthes with 20 species that inhabit freshwater, estuarine and coastal environments. Pejerrey Odontesthes argentinensis is widely distributed in coastal and estuarine areas of the Atlantic Ocean and is known to foray into estuaries of river systems, particularly in conditions of elevated salinity. However, to our knowledge, a landlocked self-sustaining population has never been recorded. In this study, we examined the pejerrey population of Salada de Pedro Luro Lake (south-east of Buenos Aires Province, Argentina) to clarify its taxonomic identity. An integrative taxonomic analysis based on traditional meristic, landmark-based morphometrics and genetic techniques suggests that the Salada de Pedro Luro pejerrey population represents a novel case of physiological and morphological adaptation of a marine pejerrey species to a landlocked environment and emphasises the environmental plasticity of this group of fishes.     

Revisiting the coupling of fatty acid to phospholipid synthesis in bacteria with FapR regulation

A key aspect in membrane biogenesis is the coordination of fatty acid to phospholipid synthesis rates. In most bacteria, PlsX is the first enzyme of the phosphatidic acid synthesis pathway, the common precursor of all phospholipids. Previously, we proposed that PlsX is a key regulatory point that synchronizes the fatty acid synthase II with phospholipid synthesis in Bacillus subtilis. However, understanding the basis of such coordination mechanism remained a challenge in Gram-positive bacteria. Here, we show that the inhibition of fatty acid and phospholipid synthesis caused by PlsX depletion leads to the accumulation of long-chain acyl-ACPs, the end products of the fatty acid synthase II. Hydrolysis of the acyl-ACP pool by heterologous expression of a cytosolic thioesterase relieves the inhibition of fatty acid synthesis, indicating that acyl-ACPs are feedback inhibitors of this metabolic route. Unexpectedly, inactivation of PlsX triggers a large increase of malonyl-CoA leading to induction of the fap regulon. This finding discards the hypothesis, proposed for B. subtilis and extended to other Gram-positive bacteria, that acyl-ACPs are feedback inhibitors of the acetyl-CoA carboxylase. Finally, we propose that the continuous production of malonyl-CoA during phospholipid synthesis inhibition provides an additional mechanism for fine-tuning the coupling between phospholipid and fatty acid production in bacteria with FapR regulation.     

Direct seeding of Brazilian savanna trees: effects of plant cover and fertilization on seedling establishment and growth

Direct seeding is a promising technique for ecological restoration, but it has been poorly studied in neotropical savannas. Different types of plant cover (no cover, crops, or green manure) and fertilization (unfertilized, synthetic fertilizer, or poultry litter) were used to verify if survival and growth of different tree species after direct seeding could be enhanced by the use of any combination of these techniques. Seedling emergence, establishment, and growth were followed for 2 years for six savanna tree species sown in an agricultural field in Central Brazil. Germination was high (52%, on average) for Anacardium occidentale, Aspidosperma macrocarpon, Hymenaea stigonocarpa, Dipteryx alata, Eugenia dysenterica, and Magonia pubescens. Six additional species were planted, but less than 5% of these seeds germinated. Crops (60% shade) did not affect seedling survival and biomass compared with the control treatment, supporting the use of this strategy during the initial phase of restoration to involve farmers in the process. In contrast, the excessive shading (95%) from the green manure treatment decreased the survival of two species and the growth in biomass and diameter of five species, especially when combined with fertilization. Seedling growth was very slow throughout the experiment, requiring extended weed management. This study supports the use of direct seeding of the studied species for savanna restoration, but methods could be improved to include a larger number of species.     

Muscle-bone properties after prolonged voluntary wheel running in a mouse model of dominant severe osteogenesis imperfecta

Objective:The objective of the current study is to assess the effect of a seven-week voluntary wheel running intervention on muscles and bones properties in a mouse model mimicking dominant severe osteogenesis imperfecta (OI).Methods:Female wild-type (WT) and OI (Col1a1^Jrt/+) mice either performed voluntarily wheel-running exercise for 7-weeks or remained sedentary. Running distance and speed, forelimb grip strength, isolated muscle force and fatigability as well as bone morphology and mechanical properties were assessed.Results:We demonstrate that female WT and OI mice voluntarily performed exercise, although OI mice exercised less than WT littermates. The exercise regimen increased soleus muscle masses in WT and OI but increased relative grip strength in WT mice only. Specific muscle force and fatigability were similar between WT and OI mice and did not improve with exercise. Furthermore, the exercise regimen did not improve the femoral architectural and biomechanical properties in OI mice.Conclusion:Our study suggests that voluntary wheel running is not appropriate to assess the effects of exercise in a mouse model of OI. Findings from exercising OI mice model studies may not necessarily be transferable to humans.     

uPA binding increases UPAR localization to lipid rafts and modifies the receptor microdomain composition

UPAR is a GPI anchored protein, which is found in both lipid rafts and in more fluid regions of the plasma membrane. We have studied the role of the ligand uPA on uPAR localization and on the composition of the lipid membrane microdomains. We have analyzed the glycosphingolipid environment of uPAR in detergent resistant membrane (DRM) fractions prepared by cell lysis with 1% Triton X-100 and fractionated by sucrose gradient centrifugation obtained from HEK293-uPAR cells. The uPAR specific lipid membrane microdomain has been separated from the total DRM fraction by immunoprecipitation with an anti-uPAR specific antibody under conditions that preserve membrane integrity. We have also tested uPA-induced ERK phosphorylation in the presence of methyl-beta-cyclodextrin, which is known to disrupt lipid rafts by sequestering cholesterol from such domains. Our results show that uPAR is partially associated with DRM and this association is increased by ligands, is independent of the catalytic activity of uPA, and is required for intracellular signalling. In the absence of ligands, uPAR experiences a lipid environment very similar to that of total DRM, enriched in sphingomyelin and glycosphingolipids. However, after treatment of cells with uPA or ATF the lipid environment is strongly impoverished of neutral glycosphingolipids.