The complex quantitative barley–<Emphasis Type="Italic">Rhynchosporium secalis</Emphasis> interaction: newly identified QTL may represent already known resistance genes

Two barley populations, i.e. 135 doubled haploid (DH) lines of the cross 'Igri' (rrs1) x 'Triton' (Rrs1) (I x T) and 76 DH lines of the cross 'Post' x 'Vixen' (both rrs1) (P x V), were analysed to identify QTL for Rhynchosporium secalis resistance independent of the Rrs1 locus by using the single spore R. secalis isolate 271 (Rrs1-virulent). A major QTL with its positive allele derived from cv. 'Triton' was detected in the I x T population on chromosome 2HS explaining almost 80% of the phenotypic variance. Thus, it can be considered as an R-gene corresponding to the already described Rrs15(CI8288) on chromosome 2HS. In addition, two minor QTL were identified, one in the centromeric region of 6H in a highly polymorphic region with already several mapped R-genes and a second one at the end of the short arm of chromosome 7H which may be an allele of Rrs2 because of its chromosomal position. Regarding the DH population P x V different minor QTL were identified on chromosomes 6H and 7H. The first one is corresponding to the genomic region of the Rrs13 gene whereas the QTL on chromosome 7H maps in a genomic region where several R-genes against different pathogens have been localized. A comparison of both QTL analyses reveals no R. secalis isolate 271-specific resistance locus but leads to the hypothesis that two of the identified QTL may be alleles of the R-genes Rrs15(CI8288) and Rrs2.     

Biophysics of ceramide signaling: interaction with proteins and phase transition of membranes

Ceramides have been implied in intracellular signal transduction systems regulating cellular differentiation, activation, survival and apoptosis and thus appear capable of changing the life style of virtually any cell type. Ceramide belongs to the group of sphingosine-based lipid second messenger molecules that are critically involved in the regulation of diverse cellular responses to exogenous stimuli. The emerging picture suggests that coupling of ceramide to specific signaling cascades is both stimulus and cell-type specific and depends on the subcellular topology of its production. However, little is understood about the molecular mode of ceramide action. In particular, in lieu of a defined ceramide binding motif it is not clear how ceramide would directly interact with putative target signaling proteins. This article proposes two modes of ceramide action. First, a protruding alkyl chain of ceramide may interact with a hydrophobic cavity of a signaling protein providing a lipid anchor to attach proteins to membranes. Second, the generation of ceramide generally increases the volume of hydrocarbon chains within the lipid bilayer thereby enhancing its propensity of to form a hexagonal II phase (Hex II). Besides the generation of a hydrophobic interaction site for proteins local hexagonal phase II formation can also change the membrane fluidity and permeability, which may impinge on membrane fusion processes, solubilization of detergent-resistant signaling rafts, or membrane receptor internalization. Thus, ceramide production by sphingomyelinases (SMase) can play a pivotal signaling role through direct interaction with signaling proteins or through facilitating the formation and trafficking of signal transduction complexes.     

Glutamatergic elements in an excitability and circumnutation mechanism

In plants, an electrical potential and circumnutation disturbances are a part of a response to environmental and internal stimuli. Precise relations between electrical potential changes and circumnutation mechanisms are unclear. We have found recently that glutamate (Glu) injection into Helianthus annuus stem induced a series of action potentials (APs) and a transient decrease in circumnutation activity. A theoretical explanation for this finding is discussed here taking into considerations data about the ion mechanism of AP and circumnutation as well as about the metabolic and signaling pathways of glutamate and their possible interactions.Key words: action potential, circumnutation, elongation, glutamate, Helianthus annuus, plant movement     

Preparation and Enantioselectivity Binding Studies of a New Chiral Cobalt(II)porphyrin‐Tröger's Base Conjugate

A new bis[cobalt(II)porphyrin]‐Tröger's base conjugate was studied as a potential receptor for methyl esters of several amino acids. The conjugate was prepared as racemate, and then resolved via preparative high‐performance liquid chromatography (HPLC) on a chiral column. The high affinity to lysine, histidine, and proline methyl esters was found by complexation studies followed by UV‐Vis spectroscopy. The studies of pure enantiomers, followed by UV‐Vis and electronic circular dichroism spectroscopy, revealed the highest enantioselectivity for lysine methyl ester. Chirality 26:361–367, 2014. © 2014 Wiley Periodicals, Inc.     

Cytogenetic evidence for diversity of two nuclei within a single diplomonad cell of <Emphasis Type="Italic">Giardia</Emphasis>

Giardia intestinalis is an ancient protist that causes the most commonly reported human diarrheal disease of parasitic origin worldwide. An intriguing feature of the Giardia cell is the presence of two morphologically similar nuclei, generally considered equivalent, in spite of the fact that their karyotypes are unknown. We found that within a single cell, the two nuclei differ both in the number and the size of chromosomes and that representatives of two major genetic groups of G. intestinalis possess different karyotypes. Odd chromosome numbers indicate aneuploidy of Giardia nuclei, and their stable occurrence is suggestive of a long-term asexuality. A semi-open type of Giardia mitosis excludes a chromosome interfusion between the nuclei. Differences in karyotype and DNA content, and cell cycle-dependent asynchrony are indicative of diversity of the two Giardia nuclei.     

Blood System Formation in the Urochordate Ciona intestinalis Requires the Variable Receptor vCRL1

Adaptive immune systems are present only in vertebrates. How do all the remaining animals withstand continuous attacks of permanently evolving pathogens? Even in the absence of adaptive immunity, every organism must be able to unambiguously distinguish "self" cells from any imaginable "nonself." Here, we analyzed the function of highly polymorphic gene vCRL1, which is expressed in follicle and blood cells of Ciona intestinalis, pointing to possible recognition roles either during fertilization or in immune reactions. By using segregation analysis, we demonstrate that vCRL1 locus is not involved in the control of self-sterility. Interestingly, genetic knockdown of vCRL1 in all tissues or specifically in hemocytes results in a drastic developmental arrest during metamorphosis exactly when blood system formation in Ciona normally occurs. Our data demonstrate that vCRL1 gene might be essential for the establishment of a functional blood system in Ciona. Presumably, presence of the vCRL1 receptor on the surface of blood cells renders them as self, whereas any cell lacking it is referred to as nonself and will be consequently destroyed. We propose that individual-specific receptor vCRL1 might be utilized to facilitate somatic self/nonself discrimination.     

Metabolism of 2-deoxy-2-fluoro-D-[3H]glucose and 2-deoxy-2-fluoro-D-[3H]mannose in yeast and chick-embryo cells.

2-Deoxy-2-fluoro-D-[3H]glucose and 2-deoxy-2-fluoro-D-[3H]mannose have been prepared by tritiation of the corresponding unlabeled 2-fluoro sugars. The tritiated 2-fluoro sugars are phosphorylated and activated by UTP and by GTP to yield UDP-2-deoxy-2-fluoro-D-[3H]glucose, UDP-2-deoxy-2-fluoro-D-[3H]mannose, GDP-2-deoxy-2-fluoro-D-[3H]glucose and GDP-2-deoxy-2-fluoro-D-[3H]mannose in both cell types. The nucleotide derivatives could also be labeled in the nucleotide moiety by feeding the cells with [14C]uridine or [14C]guanosine in the presence of unlabeled 2-fluoro sugar. No evidence was obtained for metabolic steps in which the six-carbon chain of 2-fluoro sugars was not preserved. No epimerisation of the label to 2-deoxy-2-fluoro-D-[3H]galactose could be observed by radioactive gas-liquid chromatography of the enzymatic cleavage products of the different 2-fluoro sugar metabolites isolated from either cell type. Yeast and chick embryo cells both incorporate 2-deoxy-2-fluoro-D-[3H]glucose and 2-deoxy-2-fluoro-D-[3H]mannose specifically into glycoproteins, although this incorporation is very low when compared to the incorporation of 2-deoxy-D-[3H]glucose.     

Studies on mode of action of a bacteriocin from Clostridium septicum.

A bacteriocin was found in the supernatant fluid of Clostridium septicum strain Ovinus. Sensitivity to the bacteriocin was confined to other strains of C. septicum and to strains of C. chauvoei; the other Gram-positive and Gram-negative bacteria tested for sensitivity were unaffected by the bacteriocin. The bacteriocin killed sensitive cells rapidly but cell lysis did not appear to be involved. The bacteriocin inhibited protein and RNA synthesis immediately after its addition to sensitive cells; DNA synthesis was inhibited 10 min later.