A specific subset of transient receptor potential vanilloid-type channel subunits in Caenorhabditis elegans endocrine cells function as mixed heteromers to promote neurotransmitter release

Transient receptor potential (TRP) channel subunits form homotetramers that function in sensory transduction. Heteromeric channels also form, but their physiological subunit compositions and functions are largely unknown. We found a dominant-negative mutant of the C. elegans TRPV (vanilloid-type) subunit OCR-2 that apparently incorporates into and inactivates OCR-2 homomers as well as heteromers with the TRPV subunits OCR-1 and -4, resulting in a premature egg-laying defect. This defect is reproduced by knocking out all three OCR genes, but not by any single knockout. Thus a mixture of redundant heteromeric channels prevents premature egg laying. These channels, as well as the G-protein G alpha(o), function in neuroendocrine cells to promote release of neurotransmitters that block egg laying until eggs filling the uterus deform the neuroendocrine cells. The TRPV channel OSM-9, previously suggested to be an obligate heteromeric partner of OCR-2 in sensory neurons, is expressed in the neuroendocrine cells but has no detectable role in egg laying. Our results identify a specific set of heteromeric TRPV channels that redundantly regulate neuroendocrine function and show that a subunit combination that functions in sensory neurons is also present in neuroendocrine cells but has no detectable function in these cells.     

Long term effects of manure, charcoal and mineral fertilization on crop production and fertility on a highly weathered Central Amazonian upland soil

Application of organic fertilizers and charcoal increase nutrient stocks in the rooting zone of crops, reduce nutrient leaching and thus improve crop production on acid and highly weathered tropical soils. In a field trial near Manaus (Brazil) 15 different amendment combinations based on equal amounts of carbon (C) applied through chicken manure (CM), compost, charcoal, and forest litter were tested during four cropping cycles with rice (Oryza sativa L.) and sorghum (Sorghum bicolor L.) in five replicates. CM amendments resulted in the highest (P < 0.05) cumulative crop yield (12.4 Mg ha⁻¹) over four seasons. Most importantly, surface soil pH, phosphorus (P), calcium (Ca), and magnesium (Mg) were significantly enhanced by CM. A single compost application produced fourfold more grain yield (P < 0.05) than plots mineral fertilized in split applications. Charcoal significantly improved plant growth and doubled grain production if fertilized with NPK in comparison to the NPK-fertilizer without charcoal (P < 0.05). The higher yields caused a significantly greater nutrient export in charcoal-amended fields, but available nutrients did not decrease to the same extent as on just mineral fertilized plots. Exchangeable soil aluminum (Al) was further reduced if mineral fertilizer was applied with charcoal (from 4.7 to 0 mg kg⁻¹). The resilience of soil organic matter (SOM) in charcoal amended plots (8 and 4% soil C loss, mineral fertilized or not fertilized, respectively) indicates the refractory nature of charcoal in comparison to SOM losses over 20 months in CM (27%), compost amended (27%), and control plots (25% loss).     

Assessing the role of body mass and sex on apparent adult survival in polygynous passerines: a case study of cetti's warblers in central Portugal

Adult survival, an important fitness component, is usually 1) lower in lighter individuals due to their reduced ability to survive winter conditions compared to heavier ones, especially in resident species at northern temperate latitudes and 2) lower in females compared with males due to higher reproductive costs incurred by females. In this paper, a capture–mark–recapture dataset of 649 cetti's warblers Cettia cetti ringed seasonally at two wetlands in central Portugal over an 11‐yr period (2000–2010) was modelled in a multi‐state framework to examine the influence of these individual covariates on apparent adult survival, while controlling for the presence of transient individuals in our study area. The probability of change in mass state (ψ_{Light→Heavy}, ψ_{Heavy→Light}) during the annual cycle was also estimated. Overall, birds survived better during spring–summer (breeding/moulting periods) compared with autumn–winter, but there was no effect of body mass on apparent adult survival probability. The modelling detected a significant interaction between sex and season, in which resident females survived better than resident males in spring–summer (?_RF= 0.857 ± 0.117 and ?_RM= 0.698 ± 0.181) while the opposite pattern was found in autumn–winter (?_RM= 0.440 ± 0.086 and ?_RF= 0.339 ± 0.084). In addition, cetti's warblers had a tendency to lose mass in spring–summer (ψ_{Heavy → Light}= 0.560 ± 0.063) and to regain mass in autumn–winter (ψ_{Light→Heavy}= 0.701 ± 0.069). This pattern of body mass change during the annual cycle may reflect energetic costs to reproduction and moulting, and/or a response to increased starvation risk during winter. High body mass, however, did not increase adult survival in this population presumably due to the relatively mild winter weather prevailing in central Portugal. Survival estimates are more likely to be explained by important ecological and behavioural differences between the two sexes in polygynous passerines. Our results highlight that studies aiming to identify the main factors shaping survival and individual fitness in polygynous species should be conducted during different phases of their annual cycle.     

Water potentials for developing cladodes and fruits of a succulent plant, including xylem-versus-phloem implications for water movement

Developing cladodes had lower water potentials and developingfruits had higher water potentials than the underlying cladodesof the widely cultivated prickly pear cactus, Opuntia ficus-indica.The 0.06 MPa lower value in 4-week-old daughter cladodes indicateda typical water potential gradient from the underlying clad-odealong the xylem of –0.2 MPa m^–1; the 0.17 MPa highervalue in 4-week-old fruits, which decreased to 0.07 MPa by 10weeks, implicated the phloem as their supplier of water. Thephloem sap of the underlying cladodes had an osmotic pressureof only 0.90 to 0.98 MPa, so the phloem could supply a relativelydilute solution to the photosynthetically dependent fruits (daughtercladodes of O. ficus-indica are photosynthetically independentat 4 weeks). Although the water potentials were similar foradjacent tissues, the osmotic pressures were lower for the water-storagecompared with the photosynthetic tissue; the osmotic pressureswere higher for xylem sap from fruits, for which xylary flowapparently occurred toward the underlying cladodes, than fordaughter cladodes. The relative capacitance (change in relativewater content divided by change in tissue water potential) wasapproximately 0.71 MPa^–1 for the water-storage tissueand the photosynthetic tissue of both daughter cladodes andfruits at 4 weeks of age. When these organs approached maturityat 10 weeks, the relative capacitance increased about 40% fortheir water-storage tissue, but decreased 30% for their photosynthetictissue. As the plant water content decreases during drought,about twice as much water will thus be lost per unit volumeof the water-storage tissue compared with the photosynthetictissue of maturing fruits and cladodes. Key words: Opuntia ficus-indica, phloem, relative water content, water capacitance, water potential     

The sesquiterpene botrydial produced by Botrytis cinerea induces the hypersensitive response on plant tissues and its action is modulated by salicylic acid and jasmonic acid signaling

Botrytis cinerea, as a necrotrophic fungus, kills host tissues and feeds on the remains. This fungus is able to induce the hypersensitive response (HR) on its hosts, thus taking advantage on the host's defense machinery for generating necrotic tissues. However, the identity of HR effectors produced by B. cinerea is not clear. The aim of this work was to determine whether botrydial, a phytotoxic sesquiterpene produced by B. cinerea, is able to induce the HR on plant hosts, using Arabidopsis thaliana as a model. Botrydial induced the expression of the HR marker HSR3, callose deposition, and the accumulation of reactive oxygen species and phenolic compounds. Botrydial also induced the expression of PR1 and PDF1.2, two pathogenesis-related proteins involved in defense responses regulated by salicylic acid (SA) and jasmonic acid (JA), respectively. A. thaliana and tobacco plants defective in SA signaling were more resistant to botrydial than wild-type plants, as opposed to A. thaliana plants defective in JA signaling, which were more sensitive. It can be concluded that botrydial induces the HR on its hosts and its effects are modulated by host signaling pathways mediated by SA and JA.     

Post‐dispersal seed recovery by animals: is it a plant‐ or an animal‐driven process?

The ability of animals to find and consume hoarded seeds (i.e. seed recovery) is a key stage within the seed dispersal process. However, the ecology of seed recovery is still poorly understood. Here, we analyze the factors controlling seed recovery by scatter‐hoarding rodents in an oak‐dominated temperate forest. We examined the relative importance of intrinsic seed traits (i.e. plant‐driven) and extrinsic seed factors (i.e. animal‐driven) on the probability of seed recovery. We found that seed recovery is mainly driven by extrinsic seed factors, mostly related to animal behavior (pilfering frequency, microsite preference, predation risk, burial depth and cache size). Important intrinsic traits such as seed size, seed quality and seed‐drop timing were, on average, of lower significance in the probability of seed recovery (2.8‐times less important than extrinsic factors); only seed quality was an important intrinsic trait. On the other hand, larger and nutritionally more valuable seeds showed a removal–recovery tradeoff as they enhance seed removal and hoarding (increasing dispersal quality) but also favour seed recovery (increasing predation). We find that other mechanisms beyond seed traits (e.g. masting) are needed to decrease seed recovery and, thus, increase seed survival. We conclude that, as seed recovery is mostly driven by animal behavioural factors, it substantially differs from other previous stages of the seed dispersal process that are more dependent on seed traits. We argue that seed recovery needs further attention to advance our understanding of the ecology of seed dispersal and the role of secondary dispersers as a selective force for seeds.     

Material and mechanical properties of bones deficient for fibrillin-1 or fibrillin-2 microfibrils

The contribution of non-collagenous components of the extracellular matrix to bone strength is largely undefined. Here we report that deficiency of fibrillin-1 or fibrillin-2 microfibrils causes distinct changes in bone material and mechanical properties. Morphometric examination of mice with hypomorphic or null mutations in fibrillin-1 or fibrillin-2, respectively, revealed appreciable differences in the postnatal shaping and growth of long bones. Fourier transform infrared imaging spectroscopy indicated that fibrillin-1 plays a predominantly greater role than fibrillin-2 in determining the material properties of bones. Biomechanical tests demonstrated that fibrillin-2 exerts a greater positive influence on the mechanical properties of bone than fibrillin-1 assemblies. Published evidence indirectly supports the notion that the above findings are mostly, if not exclusively, related to the differential control of TGFβ family signaling by fibrillin proteins. Our study therefore advances our understanding of the role that extracellular microfibrils play in bone physiology and implicitly, in the pathogenesis of bone loss in human diseases caused by mutations in fibrillin-1 or -2.     

Fine-Scale Population Structure of Blue Whale Wintering Aggregations in the Gulf of California

Population differentiation in environments without well-defined geographical barriers represents a challenge for wildlife management. Based on a comprehensive database of individual sighting records (1988–2009) of blue whales from the winter/calving Gulf of California, we assessed the fine-scale genetic and spatial structure of the population using individual-based approaches. Skin samples of 187 individuals were analyzed for nine microsatellite loci. A single population with no divergence among years and months and no isolation by distance (Rxy = 0.1–0.001, p>0.05) were found. We ran two Bayesian clustering methods using Structure and Geneland softwares in two different ways: 1) a general analysis including all individuals in which a single cluster was identified with both softwares; 2) a specific analysis of females only in which two main clusters (Loreto Bay and northern areas, and San Jose-La Paz Bay area) were revealed by Geneland program. This study provides information indicating that blue whales wintering in the Gulf of California are part of a single population unit and showed a fine-scale structure among females, possibly associated with their high site fidelity, particularly when attending calves. It is likely that the loss of genetic variation is minimized by male mediated gene flow, which may reduce the genetic drift effect. Opportunities for kin selection may also influence calf survival and, in consequence, have a positive impact on population demography in this small and endangered population.     

Specificity of binding of the plectin actin-binding domain to beta4 integrin

Plectin is a major component of the cytoskeleton and links the intermediate filament system to hemidesmosomes by binding to the integrin beta4 subunit. Previously, a binding site for beta4 was mapped on the actin-binding domain (ABD) of plectin and binding of beta4 and F-actin to plectin was shown to be mutually exclusive. Here we show that only the ABDs of plectin and dystonin bind to beta4, whereas those of other actin-binding proteins do not. Mutations of the ABD of plectin-1C show that Q131, R138, and N149 are critical for tight binding of the ABD to beta4. These residues form a small cavity, occupied by a well-ordered water molecule in the crystal structure. The beta4 binding pocket partly overlaps with the actin-binding sequence 2 (ABS2), previously shown to be essential for actin binding. Therefore, steric interference may render binding of beta4 and F-actin to plectin mutually exclusive. Finally, we provide evidence indicating that the residues preceding the ABD in plectin-1A and -1C, although unable to mediate binding to beta4 themselves, modulate the binding activity of the ABD for beta4. These studies demonstrate the unique property of the plectin-ABD to bind to both F-actin and beta4, and explain why several other ABD-containing proteins that are expressed in basal keratinocytes are not recruited into hemidesmosomes.