Protoplasts fromPodospora anserina: Isolation,purification, and transformation

Protoplasts fromPodospora anserina mycelium were produced using the commercially available enzyme Novozym 234. Different parameters involved in protoplast isolation were analyzed in order to establish optimal conditions, and protoplast production was notably increased. For the purification of protoplasts, several techniques based on both centrifugation and filtration were assayed, with filtration yielding the best results. Regeneration of protoplasts was studied on different media and osmostic stabilizers, and about 80% regeneration was obtained. The good physiological condition of the protoplasts produced with this method is demonstrated by the lack of cell wall and high regeneration rate and transformation frequencies.     

Causal modeling in a multi-omic setting: insights from GAW20

Background

The GAW20 group formed on the theme of methods for association analyses of repeated measures comprised 4sets of investigators. The provided “real” data set included genotypes obtained from a human whole-genome association study based on longitudinal measurements of triglycerides (TGs) and high-density lipoprotein in addition to methylation levels before and after administration of fenofibrate. The simulated data set contained 200 replications of methylation levels and posttreatment TGs, mimicking the real data set.

Results

The different investigators in the group focused on the statistical challenges unique to family-based association analyses of phenotypes measured longitudinally and applied a wide spectrum of statistical methods such as linear mixed models, generalized estimating equations, and quasi-likelihood–based regression models. This article discusses the varying strategies explored by the group’s investigators with the common goal of improving the power to detect association with repeated measures of a phenotype.

Conclusions

Although it is difficult to identify a common message emanating from the different contributions because of the diversity in the issues addressed, the unifying theme of the contributions lie in the search for novel analytic strategies to circumvent the limitations of existing methodologies to detect genetic association.

     

SEASONAL VARIATIONS IN PHOTOSYNTHESIS-IRRADIANCE RESPONSES BY BIOFILMS IN MEDITERRANEAN STREAMS

The relationships between primary production and irradiance were analyzed over an annual cycle in natural biofilms of two undisturbed streams: La Solana (LS), an open calcareous stream, and Riera Major (RM), a shaded siliceous stream. In LS, low photosynthetic efficiency (α^chl and α^area) and high values of both the light saturation parameter (I_k) and the carotenoid / chlorophyll ratio indicated adaptation to high light regimes. On the other hand, higher photosynthetic efficiency and lower I_k as well as photoinhibition at high irradiance found in the biofilms of RM indicated shade adaptation. However, the lack of correlation between light availability in nature and the photosynthetic parameters studied in the laboratory suggested that light was not the most important factor in determining seasonal changes in the photosynthetic behavior in this stream. Both in the open and shaded streams, algal patches collected simultaneously exhibited different photosynthesis-irradiance (P-I) curues, showing that community composition influenced the P-I parameters. In the open stream (LS), however, significant negative correlations between α^area and chlorophyll a and between P _max^chl and chlorophyll a ( r = -0.994 , P < 0.001, and r = -0.929 , P < 0.05, respectively) suggested that photosynthesis was affected by self-shading. Due to the absence of photoinhibition in the biofilms of LS, high photosynthetic rates were maintained at the ambient high light environment, thus compensating for low photosynthesis at low irradiance. In the shaded stream (RM), because photosynthesis was saturated at low irradiances, primary production was relatively high given the low light conditions .     

Ecology and morphological variability of Aulacoseira granulata (Bacillariophyceae) in Spanish reservoirs

The ecology of Aulacoseira (formerly Melosira) granulata andits different forms in     

Sustained accumulation of methyl salicylate alters antioxidant protection and reduces tolerance of holm oak to heat stress

Methyl salicylate (MeSA) is thought to have a major role in biotic and abiotic stresses by acting as a signal to trigger the oxidative burst, which is needed to activate gene expression in plant stress responses. To assess the potential effects of sustained foliar accumulation of MeSA on plant stress tolerance, the extent of photo- and antioxidant protection, lipid peroxidation and visual leaf area damage were evaluated in MeSA-treated ( c. 60 nl l⁻¹ in air) and control holm oak ( Quercus ilex L.) plants exposed to heat stress. Control plants showed an increase in foliar MeSA levels up to 1.8 nmol [gDW]⁻¹ as temperature increased and they displayed tolerance to temperatures as high as 45°C, which might be attributed, at least in part, to enhanced xanthophyll de-epoxidation and increases in ascorbate and α-tocopherol. MeSA-treated plants showed a sustained foliar accumulation of this compound, with values ranging from 10 to 23 nmol [gDW]⁻¹ throughout the experiment. These plants showed lower ascorbate and tocopherol levels and higher oxidative damage at 50°C than controls, as indicated by enhanced malondialdehyde levels and leaf area damage and lower maximum efficiency of PSII photochemistry ( F _v/ F _m ratio). These results demonstrate that a sustained foliar accumulation of MeSA is detrimental to plant function and that it can reduce thermotolerance in holm oak by altering antioxidant defences.     

Flow regulation increases food‐chain length through omnivory mechanisms in a Mediterranean river network

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