Restoration of Dry Afromontane Forest Using Pioneer Shrubs as Nurse-Plants for Olea europaea ssp. cuspidata

Shrubs are often considered competitive barriers for seedlings planted in reforestation programs, although they can facilitate tree recruitment, especially in ecosystems under high abiotic stress. An alternative reforestation technique using pioneer shrubs as nurse‐plants for Olea europaea ssp. cuspidata was tested in exclosures in northern Ethiopia. Seedlings were planted in three different microhabitats, and their survival was monitored. The microhabitats were bare soil patches between shrubs, patches under the dominant shrub Acacia etbaica, and patches under Euclea racemosa, an evergreen shrub, which supports the majority of naturally established Olea recruits. The ability of shrubs to offer protection against browsing goats was tested experimentally. Controlled shading was used to determine whether solar irradiation causes seedling mortality in environments without water stress. Data were analyzed using Kaplan–Meier survival analysis, Kruskal–Wallis analysis of variance (ANOVA), and one‐way ANOVA. Olea survival was significantly higher and shoot damage by goats was lower when planted under shrub cover compared to bare soil patches, particularly under Euclea canopies, although high shade levels reduced seedling performance. Reduction of solar radiation by shrub canopies and thus control of soil–water evaporation and seedling transpiration most likely controlled the observed facilitation. Planting under shrubs may increase seedling survival and assist regeneration of dry Afromontane vegetation. Preserving pioneers also reduces soil erosion and conserves biodiversity. Excluding livestock is essential for Olea woodland restoration and allows persistent but morphologically modified Olea shrubs to develop vigorous regrowth. Facilitative processes are guiding principles for assisted forest restoration, but above‐average rains may be critical to restore higher biomass levels in semiarid areas.     

Differential timing of gene expression regulation between leptocephali of the two Anguilla eel species in the Sargasso Sea

The unique life-history characteristics of North Atlantic catadromous eels have long intrigued evolutionary biologists, especially with respect to mechanisms that could explain their persistence as two ecologically very similar but reproductively and geographically distinct species. Differential developmental schedules during young larval stages have commonly been hypothesized to represent such a key mechanism. We performed a comparative analysis of gene expression by means of microarray experiments with American and European eel leptocephali collected in the Sargasso Sea in order to test the alternative hypotheses of (1) differential timing of gene expression regulation during early development versus (2) species-specific differences in expression of particular genes. Our results provide much stronger support for the former hypothesis since no gene showed consistent significant differences in expression levels between the two species. In contrast, 146 genes showed differential timings of expression between species, although the observed expression level differences between the species were generally small. Consequently, species-specific gene expression regulation seems to play a minor role in species differentiation. Overall, these results show that the basis of the early developmental divergence between the American and European eel is probably influenced by differences in the timing of gene expression regulation for genes involved in a large array of biological functions.     

Molecular detection of Puccinia horiana Henn. the causal agent of Chrysanthemum white rust

Chrysanthemum white rust is one of the most important foliar diseases of pot chrysanthemum and is a quarantine pathogen in many countries. Under conducive environmental conditions, it has the potential to completely destroy susceptible cultivars. This is mainly avoided through frequent preventive fungicide applications. As part of a research program to develop a disease warning system, a molecular detection method was developed. To determine the nucleotide sequence of the nuclear rDNA-ITS (internal transcribed spacer) region of P. horiana, 56 isolates were collected between 2003 and 2006 from diseased commercial chrysanthemum plants from different national and international geographical areas. DNA was isolated from the basidiospores or teliospores from several isolates and the rDNA-ITS region was cloned and sequenced. Based on the limited variability in rDNA-ITS sequence between these isolates, several primer pairs were designed and tested for detection through conventional and real-time PCR. Specificity of detection was cross-checked against a variety of other fungi (saprophytes and other rusts) that may occur in the same environment, and against DNA of healthy chrysanthemum leaves. Using the best primers, the PCR-based methods successfully detected all the P. horiana isolates tested, while no signal was observed with other rust species up to 1 ng non target genomic DNA template. The limit of detection of P. horiana DNA in conventional, nested and real-time PCR was 10 pg, 10 fg and 10 fg, respectively. The DNA extraction method and PCR template concentration were optimized to maximize the recoverability of the pathogen from infected plant tissue. Using the optimized real-time PCR method, the pathogen could be detected in washed plant tissue, 9 hours after inoculation. Hence, this method allows detection of the P. horiana in any part of its latent stage and will also serve as a tool for studying the biology and epidemiology of the pathogen.     

In chronic fatigue syndrome, the decreased levels of omega-3 poly-unsaturated fatty acids are related to lowered serum zinc and defects in T cell activation

There is now evidence that major depression is accompanied by decreased levels of omega3 poly-unsaturated fatty acids (PUFA), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). There is a strong comorbidity between major depression and chronic fatigue syndrome (CFS). The present study has been carried out in order to examine PUFA levels in CFS. In twenty-two CFS patients and 12 normal controls we measured serum PUFA levels using gas chromatography and mass spectrometry. We found that CFS was accompanied by increased levels of omega6 PUFAs, i.e. linoleic acid and arachidonic acid (AA), and mono-unsaturated fatty acids (MUFAs), i.e. oleic acid. The EPA/AA and total omega3/omega6 ratios were significantly lower in CFS patients than in normal controls. The omega3/omega6 ratio was significantly and negatively correlated to the severity of illness and some items of the FibroFatigue scale, i.e. aches and pain, fatigue and failing memory. The severity of illness was significantly and positively correlated to linoleic and arachidonic acid, oleic acid, omega9 fatty acids and one of the saturated fatty acids, i.e. palmitic acid. In CFS subjects, we found significant positive correlations between the omega3/omega6 ratio and lowered serum zinc levels and the lowered mitogen-stimulated CD69 expression on CD3+, CD3+ CD4+, and CD3+ CD8+ T cells, which indicate defects in early T cell activation. The results of this study show that a decreased availability of omega3 PUFAs plays a role in the pathophysiology of CFS and is related to the immune pathophysiology of CFS. The results suggest that patients with CFS should respond favourably to treatment with--amongst other things--omega3 PUFAs, such as EPA and DHA.     

Morphological and genetic seasonal dynamics of European eel Anguilla anguilla recruitment in southern France

The fine scale morphological and genetic dynamics of successive waves of Anguilla anguilla glass eel recruitment was studied over a 2 year period at a southern European Mediterranean location (Camargue, France) with continuous recruitment. Using morphometric [total length (L_T), mass (M), condition (K) and pigmentation stage] as well as genetic (allozyme) markers, the aim was to test for the existence of temporally separated spawning groups and explore the relation between genetic variability and morphological heterogeneity of recruits. The results showed that L_T, M and K varied over time, being highest from the end of summer to winter (peaking in December) and lowest in spring (lowest in April). The pigmentation stages within monthly samples were highly diverse with a heterogeneous seasonal pattern. Allozyme data showed high genetic variability values within samples, but low genetic differentiation among samples (F_ST = 0·003, P < 0·05). Pairwise comparisons between samples indicated a positive correlation between genetic differentiation and difference in recruitment time (days), with a marked increase in genetic differentiation around 250 days between monthly recruitment samples. Furthermore, genetic diversity increased with the number of pigmentation stages per sample and was negatively correlated with the North Atlantic Oscillation (NAO) index during the putative year of trans‐oceanic migration. No correlation, however, was found between the level of multilocus heterozygosity (MLH) and growth variables. A situation of genetic patchiness with fluctuating parental contribution can thus best explain the patterns observed, although the existence of two separate spawning periods cannot be excluded. More discriminatory and sensitive genetic markers, such as (neutral and adaptive) microsatellites, could probably provide additional insights into the most probable hypothesis explaining the population structure and recruitment heterogeneity of A. anguilla.     

Synthesis and evaluation of the quorum sensing inhibitory effect of substituted triazolyldihydrofuranones

Acylhomoserine lactone (AHL) analogues in which the amide function is replaced by a triazole group were synthesized and evaluated for their effect on quorum sensing (QS) and biofilm formation in Burkholderia cenocepacia and Pseudomonas aeruginosa. In addition, the influence of the length of the acyl-mimicking chain was investigated. The compounds showed selectivity between two different AHL QS systems. 3-(1H-1,2,3-Triazol-1-yl)dihydrofuran-2(3H)-ones, in which the 4-substituent best resembled the acyl chain of the native AHL molecule exhibited significant QS agonistic and antagonistic activities. Replacing this aliphatic substituent by a phenyl-containing moiety resulted in active inhibitors of QS. The most active compounds showed biofilm inhibitory as well as biofilm eradicating activities in both test organisms.