A Multidimensional Functional Trait Approach Reveals the Imprint of Environmental Stress in Mediterranean Woody Communities

Water availability is one of the most important factors determining species distribution, plant community structure and ecosystem functioning. We explore how the functional structure of Mediterranean woody plant communities varies along a regional gradient of aridity in the Andalusian region (south Spain). We question whether communities located in more arid sites show more similarity in their functional structure when compared with communities located in wetter sites or whether, instead, there is divergence in their functional spaces. We selected five aridity zones (three sampling sites per zone) and measured 13 traits of different functional dimensions (including leaf, stem and root traits) in 74 woody plant species. We quantified functional space differences using the n-dimensional niche space approach (hypervolume). We found a larger functional space for the wetter communities compared with the more arid communities, which showed greater overlap of the trait space occupation. Our results indicate that aridity acts as a key abiotic filter affecting various metrics of the community trait structure, in accordance with the plant economics spectrum. We have also documented consistent variation in the functional space, supporting lower functional diversity under more harsh climatic conditions. The trend of functional space variation along the aridity gradient was different when considering traits from only one plant organ. Thus, the filtering process driving the functional structure of the communities studied here largely depends on the trait axis considered; for example, the root dimension showed considerable variation in wet environments, whereas the leaf dimension exhibited a larger functional space in the drier habitats.     

Regulation of p53 levels by the E1B 55-kilodalton protein and E4orf6 in adenovirus-infected cells.

The adenovirus type 5 243R E1A protein induces p53-dependent apoptosis in the absence of the 19- and 55-kDa E1B polypeptides. This effect appears to result from an accumulation of p53 protein and is unrelated to expression of E1B products. We now report that in the presence of the E1B 55-kDa polypeptide, the 289R E1A protein does not induce such p53 accumulation and, in fact, is able to block that induced by E1A 243R. This inhibition also requires the 289R-dependent transactivation of E4orf6 expression. E4orf6 is known to form complexes with the E1B 55-kDa protein and to function both in the transport and stabilization of viral mRNA and in shutoff of host cell protein synthesis. We demonstrated that the block in p53 accumulation is not due to the generalized shutoff of host cell metabolism. Rather, it appears to result from a mechanism targeted specifically to p53, most likely involving a decrease in the stability of p53 protein. The E1B 55-kDa protein is known to interact with both E4orf6 and p53, and as demonstrated recently by others, we showed that E4orf6 also binds directly to p53. Thus, multiple interactions between all three proteins may regulate p53 stability, resulting in the maintenance of low levels of p53 following virus infection.     

Disentangling the relative importance of species occurrence,abundance and intraspecific variability in community assembly: a trait‐based approach at the whole‐plant level in Mediterranean forests

Understanding which factors and rules govern the process of assembly in communities constitutes one of the main challenges of plant community ecology. The presence of certain functional strategies along broad environmental gradients can help to understand the patterns observed in community assembly and the filtering mechanisms that take place. We used a trait‐based approach, quantifying variations in aboveground (leaf and stem) and belowground (root) functional traits along environmental gradients in Mediterranean forest communities (south Spain). We proposed a new practical method to quantify the relative importance of species turnover (distinguishing between species occurrence and abundance) versus intraspecific variation, which allowed us to better understand the assemblage rules of these plant communities along environmental gradients. Our results showed that the functional structure of the studied plant communities was highly determined by soil environment. Results from our modelling approach based on maximum likelihood estimators showed a predominant influence of soil water storage on most of the community functional traits. We found that changes in community functional structure along environmental gradients were mainly promoted by species turnover rather than by intraspecific variability. Specifically, our new method of variance decomposition demonstrated that between‐site trait variation was the result of changes in species occurrence rather than in the abundance of certain dominant species. In conclusion, this study showed that water availability promoted the predominance of specific trait values (both in above and belowground fractions) associated to a resource acquisition or conservation strategy. In addition, we provided evidence that changes on community functional structure along the environmental gradient were mainly promoted by a process of species replacement, which represent a crucial step towards a more general understanding of the relative importance of intraspecific versus interspecific trait variation in these woody Mediterranean communities.     

DNA divergence in and around the alcohol dehydrogenase locus in five closely related species of Hawaiian Drosophila

The alcohol dehydrogenase (Adh) region from five planitibia subgroup species of Hawaiian picture-wing Drosophila has been cloned. A total of 15 kb of DNA in and around the Adh gene has been compared among the five species. Genetic distances were calculated to determine evolutionary relationships. These distances agree with previous distances determined by protein polymorphism and DNA hybridization techniques and can be interpreted in terms of specific island colonization and speciation (founder) events over the past 5 Myr. Examination of the restriction maps of the cloned Adh region from the five species shows many instances of small deletions, insertion of a transposable element in D. heteroneura, and the existence of a highly variable region on the 3' side of the Adh gene. Clustering relationships and rates of DNA change are calculated and compared with the relationship found for other species of Drosophila.      

Tissue culture response in various wild and cultivated Solanum germplasm accessions for exploitation in potato breeding

The response to different in vitro methods for use in potato breeding has been evaluated in 11 genotypes of 5 Solanum species, S. etuberosum, S. lycopersicoides, S. maglia, S. rickii, and S. tuberosum. Callus induction and growth, and shoot regeneration were strongly influenced by the genotype, explant source, and medium utilized. Furthermore, considerable differences among the 11 genotypes were found both in plating efficiency and shoot regeneration from protoplast culture. Some interesting correlations were found between different tissue culture responses, suggesting linkage and/or pleiotropic effect of genes. The potential application to potato breeding of the in vitro techniques analyzed is discussed.Abbreviations BA 6-benzylaminopurine - GA₃ gibberellic acid - NAA naphthaleneacetic acid - MS Murashige & Skoog (1962) - 2,4-d dichlorophenoxyacetic acid     

Protective Vascular and Cardiac Effects of Inducible Nitric Oxide Synthase in Mice with Hyperhomocysteinemia

Diet-induced hyperhomocysteinemia produces endothelial and cardiac dysfunction and promotes thrombosis through a mechanism proposed to involve oxidative stress. Inducible nitric oxide synthase (iNOS) is upregulated in hyperhomocysteinemia and can generate superoxide. We therefore tested the hypothesis that iNOS mediates the adverse oxidative, vascular, thrombotic, and cardiac effects of hyperhomocysteinemia. Mice deficient in iNOS (Nos2−/−) and their wild-type (Nos2+/+) littermates were fed a high methionine/low folate (HM/LF) diet to induce mild hyperhomocysteinemia, with a 2-fold increase in plasma total homocysteine (P<0.001 vs. control diet). Hyperhomocysteinemic Nos2+/+ mice exhibited endothelial dysfunction in cerebral arterioles, with impaired dilatation to acetylcholine but not nitroprusside, and enhanced susceptibility to carotid artery thrombosis, with shortened times to occlusion following photochemical injury (P<0.05 vs. control diet). Nos2−/− mice had decreased rather than increased dilatation responses to acetylcholine (P<0.05 vs. Nos2+/+ mice). Nos2−/− mice fed control diet also exhibited shortened times to thrombotic occlusion (P<0.05 vs. Nos2+/+ mice), and iNOS deficiency failed to protect from endothelial dysfunction or accelerated thrombosis in mice with hyperhomocysteinemia. Deficiency of iNOS did not alter myocardial infarct size in mice fed the control diet but significantly increased infarct size and cardiac superoxide production in mice fed the HM/LF diet (P<0.05 vs. Nos2+/+ mice). These findings suggest that endogenous iNOS protects from, rather than exacerbates, endothelial dysfunction, thrombosis, and hyperhomocysteinemia-associated myocardial ischemia-reperfusion injury. In the setting of mild hyperhomocysteinemia, iNOS functions to blunt cardiac oxidative stress rather than functioning as a source of superoxide.     

A flower with several secretions: anatomy,secretion composition,and functional aspects of the floral secretory structures of Chelonanthus viridiflorus (Helieae—Gentianaceae)

Floral secretory structures have been reported for Gentianaceae; however, morphoanatomical studies of these glands are rare. We described the development and secretory activity of the colleters and nectaries throughout the floral development of Chelonanthus viridiflorus. We collected flower buds, flowers at anthesis, and fruits to be investigated using light and scanning electron microscopy. We performed histochemical tests on the secretion of colleters and used glycophyte to confirm the presence of glucose in nectar. Colleters are located on the ventral surface of sepals and nectaries occur in four regions: (i) the dorsal and (ii) ventral surfaces of sepals; (iii) apex of petals; and (iv) base of ovary. The colleters have a short peduncle and a secretory portion with homogeneous cells. They are active in flower buds and secrete polysaccharides and proteins. In flowers at anthesis, they begin to senescence presenting protoplast retraction, cell collapse, and lignification; these characteristics are intensified in fruit. The nectaries of sepals and petals have two to five cells surrounding a central cell through which the secretion is released. Nectaries are numerous, forming a nectariferous area on the dorsal surface of sepals, like that observed on petals, and can form isolated units on the ventral surface of sepals. They are active from flower buds to fruits. A region with secretory activity was identified at the base of the ovary. The secretion of colleters acts in the protection of developing organs, while nectaries are related to defenses against herbivores and the supply of nectar to potential robbers or pollinators.

     

High-intensity Ultrasound as a Tool to Form Water in Oleogels Emulsions Structured by Lipids Oleogelators

This study aims to evaluate the structuration power and physical properties of oleogel emulsions formed by monoglycerides (MG), hardfat (HF), and lecithin (LE), with and without high-intensity ultrasound (HIU). Emulsion gels with and without HIU were prepared in mono-, bi- and ternary gelator blends (10% of the lipid phase) and with different water (W) proportions (W?=?1, 15, or 30%). All samples were analyzed according to their gel/emulsion formation, microstructure, melting behavior, rheology, texture, polymorphism, and oil binding capacity. In mono structured emulsions only MG was able to form structured emulsions that did not flow. Three synergic combinations of oleogels were found: MG:HF, HF:LE, and MG:HF:LE; nevertheless, the only synergic combination found in all water proportions was MG:HF. Sonicated MG:HF emulsions formed more organized and stable water droplets, and with 30 W even achieved similar physical properties as MG:HF oleogel (0 W). A soft structured emulsion was also found for sonicated LE and HF:LE with 30 W. Multicomponent emulsion gels formed by MG, HF, and LE are a good alternative for food applications because they can form different synergic combinations with good physical properties such as hardness (>?1 N), elastic modulus (>?1?×?10⁵ Pa), and oil binding capacity (>?99%), and these properties can be even improved by HIU.

     

Spatial patterns of soil pathogens in declining Mediterranean forests: implications for tree species regeneration

Soil-borne pathogens are a key component of the belowground community because of the significance of their ecological and socio-economic impacts. However, very little is known about the complexity of their distribution patterns in natural systems. Here, we explored the patterns, causes and ecological consequences of spatial variability in pathogen abundance in Mediterranean forests affected by oak decline. We used spatially explicit neighborhood models to predict the abundance of soil-borne pathogen species (Phytophthora cinnamomi, Pythium spiculum and Pythium spp.) as a function of local abiotic conditions (soil texture) and the characteristics of the tree and shrub neighborhoods (species composition, size and health status). The implications of pathogen abundance for tree seedling performance were explored by conducting a sowing experiment in the same locations in which pathogen abundance was quantified. Pathogen abundance in the forest soil was not randomly distributed, but exhibited spatially predictable patterns influenced by both abiotic and, particularly, biotic factors (tree and shrub species). Pathogen abundance reduced seedling emergence and survival, but not in all sites or tree species. Our findings suggest that heterogeneous spatial patterns of pathogen abundance at fine spatial scale can be important for the dynamics and restoration of declining Mediterranean forests.