Hydrogel substrate amendment alleviates drought effects on young citrus plants

Water deficits affect citrus physiology, yield, fruit size and quality. Citrus can respond to drought stress conditions through endogenous hormonal regulation of water status and leaf abscission. In this work, we assayed the efficiency of an amendment to soilless media in delaying the drought stress effect in young citrus seedlings and trees. Substrate amendment promoted plant survival of citrus seedlings subjected to several cycles of drought stress and rehydration. In budded trees, the amendment increased substrate water content, leaf water potential, leaf number, root biomass, CO₂ assimilation and stomatal conductance over that of control plants growing in non-amended substrates. We conclude that the substrate amendment reduced the damaging effects of drought stress in citrus plants. The longer survival of seedlings in the amended treatment together with the reduction in leaf abscission and the improvement of physiological parameters, can account for a higher vigour of citrus grown under water stress conditions.     

Metabolites from endophytes of the medicinal plant Erythrina crista-galli

Erythrina crista-galli (Fabaceae) is used in Argentinean ethnopharmacology as anti-inflammatory medication, narcotic, desinfectant, and for the treatment of wounds. The common name of the tree is "ceibo" or coral tree. The dominating endophytes in E. crista-galli all belong to the genus Phomopsis as identified by microscopic features and the analysis of their ITS sequences. To investigate a possible contribution of Phomopsis spp. to the metabolites found in the plant, twelve different isolates were cultivated in different media. Besides several new metabolites a number of known compounds were detected: mellein, nectriapyrone, 4-hydroxymellein, scytalone, tyrosol, clavatol, mevinic acid, and mevalonolactone.     

Male fertility in natural populations of red deer is determined by sperm velocity and the proportion of normal spermatozoa

Male reproductive success is determined by the ability of males to gain sexual access to females and by their ability to fertilize ova. Among polygynous mammals, males differ markedly in their reproductive success, and a great deal of effort has been made to understand how selective forces have shaped traits that enhance male competitiveness both before and after copulation (i.e., sperm competition). However, the possibility that males also may differ in their fertility has been ignored under the assumption that male infertility is rare in natural populations because selection against it is likely to be strong. In the present study, we examined which semen traits correlate with male fertility in natural populations of Iberian red deer (Cervus elaphus hispanicus). We found no trade-offs between semen traits. Our analyses revealed strong associations between sperm production and sperm swimming velocity, sperm motility and proportion of morphologically normal spermatozoa, and sperm viability and acrosome integrity. These last two variables had the lowest coefficients of variation, suggesting that these traits have stabilized at high values and are unlikely to be related to fitness. In a fertility trial, our results show a large degree of variation in male fertility, and differences in fertility were determined mainly by sperm swimming velocity and by the proportion of morphologically normal sperm. We conclude that male fertility varies substantially in natural populations of Iberian red deer and that, when sperm numbers are equal, it is determined mainly by sperm swimming velocity and sperm morphology.     

Application of the yeast Yarrowia lipolytica as a model to analyse human pathogenic mutations in mitochondrial complex I (NADH:ubiquinone oxidoreductase)

While diagnosis and genetic analysis of mitochondrial disorders has made remarkable progress, we still do not understand how given molecular defects are correlated to specific patterns of symptoms and their severity. Towards resolving this dilemma for the largest and therefore most affected respiratory chain enzyme, we have established the yeast Yarrowia lipolytica as a eucaryotic model system to analyse respiratory chain complex I. For in vivo analysis, eYFP protein was attached to the 30-kDa subunit to visualize complex I and mitochondria. Deletions strains for nuclear coded subunits allow the reconstruction of patient alleles by site-directed mutagenesis and plasmid complementation. In most of the pathogenic mutations analysed so far, decreased catalytic activities, elevated K(M) values, and/or elevated I(50) values for quinone-analogous inhibitors were observed, providing plausible clues on the pathogenic process at the molecular level. Leigh mutations in the 49-kDa and PSST homologous subunits are found in regions that are at the boundaries of the ubiquinone-reducing catalytic core. This supports the proposed structural model and at the same time identifies novel domains critical for catalysis. Thus, Y. lipolytica is a useful lower eucaryotic model that will help to understand how pathogenic mutations in complex I interfere with enzyme function.     

Human follicle-stimulating hormone (FSH) receptor interacts with the adaptor protein APPL1 in HEK 293 cells: potential involvement of the PI3K pathway in FSH signaling

Selection of a dominant follicle that will ovulate likely occurs by activation of cell survival pathways and suppression of death-promoting pathways in a mechanism involving FSH and its cognate receptor (FSHR). A yeast two-hybrid screen of an ovarian cDNA library was employed to identify potential interacting partners with human FSHR intracellular loops 1 and 2. Among eight cDNA clones identified in the screen, APPL1 (adaptor protein containing PH domain, PTB domain, and leucine zipper motif; also known as APPL or DIP13alpha) was chosen for further analysis. APPL1 appears to coimmunoprecipitate with FSHR in HEK 293 cells stably expressing FSHR (293/FSHR cells), confirming APPL1 as a potential FSHR-interacting partner. The phosphorylation status of members of the phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathway was also examined because of the proposed role of APPL1 in the antiapoptotic PI3K/Akt pathway. FOXO1a, also referred to as forkhead homologue in rhabdomyosarcoma, is a downstream effector in the pathway and tightly linked to expression of proapoptotic genes. FOXO1a, but not the upstream kinase Akt, is rapidly phosphorylated, and FOXO1a is thereby inactivated when 293/FSHR cells are treated with FSH. In addition, FSHR coimmunoprecipitates with Akt. The identification of APPL1 as a potential interactor with FSHR and the finding that FOXO1a is phosphorylated in response to FSH provide a possible link between FSH and PI3K/Akt signaling, which may help to delineate a survival mechanism whereby FSH selects the dominant follicle to survive.     

Evolution of sex-biased maternal effects in birds: III. Adjustment of ovulation order can enable sex-specific allocation of hormones, carotenoids, and vitamins

Overlap in growth of offspring should constrain the opportunity for sex-biased maternal effects, yet sex-specific allocation of maternal resources among simultaneously growing ova is often observed in vertebrates. In birds, such allocation can be accomplished either by temporal clustering of ova that become the same sex, resulting in sex-biased egg-laying order, or by follicle-specific delivery of maternal resources. Two house finch populations at the northern and southern boundaries of the species range have opposite ovulation sequences of male and female eggs, and thus, in the absence of sex differences in ova growth or sex-specific maternal strategies, would be expected to have opposite sex-specific accumulation of maternal products. We found that the populations had strong and similar gradients of steroid distribution in relation to ovulation order, whereas distribution of carotenoids and vitamins correlated with each follicle's accumulation of steroids. In both populations, temporal bias in production of sons and daughters within a clutch enabled strongly sex-specific acquisition of maternal products, and oocytes of the same sex were highly interdependent in their accumulation of steroids. Moreover, in nests where the sex-bias in relation to ovulation order deviated from population-specific patterns, eggs had highly distinct concentrations of steroids, carotenoids and vitamins. These results and previous findings of sex-specific yolk partitioning among oocytes suggest that oocytes that become males and females are temporally or spatially clustered during their ovarian growth. We discuss the implication of these findings for the evolution of sex-specific maternal resource allocation.     

Immobilization of enzymes in microtiter plate scale

Different immobilization methods were adapted to the 96-well microtiter plate scale using esterases as model enzymes. The methods tested were based on adsorption, coprecipitation, aggregation and covalent bonding. The protein covered microcrystals proved to be the best method in terms of yield and expressed activity for the test reaction, which was the alcoholysis of p-nitrophenyl acetate with 1-propanol under anhydrous conditions.     

Mammalian Mitochondrial DNA Replication Intermediates Are Essentially Duplex but Contain Extensive Tracts of RNA/DNA Hybrid

We demonstrate, using transmission electron microscopy and immunopurification with an antibody specific for RNA/DNA hybrid, that intact mitochondrial DNA replication intermediates are essentially duplex throughout their length but contain extensive RNA tracts on one strand. However, the extent of preservation of RNA in such molecules is highly dependent on the preparative method used. These findings strongly support the strand-coupled model of mitochondrial DNA replication involving RNA incorporation throughout the lagging strand.