Field growth characteristics of two aquatic carnivorous plants,Aldrovanda vesiculosa andUtricularia australis

Basic growth characteristics of two species of free-floating submerged carnivorous plants, the very rare and stenotopicAldrovanda vesiculosa and the very common and eurytopicUtricularia australis, were investigated in a 10/11-day field growth experiment within three nylon enclosures at two artificialAldrovanda sites in the T?eboň region, S Bohemia, Czech Republic, at the peak of a growing season. Growth ofAldrovanda was best at a meso-eutrophic site (biomass doubling time,T ₂, 8.4–10.7 days, mean growth of new leaf whorls 0.96 whorls days^?1, 1.6 developed branches per shoot) and slower at an oligo-mesotrophic site (T ₂ 17.2–21.5 days, growth of whorls 1.01 whorls days^?1, 0.1–0.5 branches per shoot). Growth ofUtricularia was similar at both sites (T ₂ 19.8–33.2 days or 9.1–16.8 days, growth of whorls 3.1 or 2.7 whorls days^?1, 1.5–2.1 or 0.8–1.4 developed branches per shoot at the former or latter site, respectively). Throughout the experiment, both species at the meso-eutrophic site allocated relatively more biomass to the production and growth of branches, than to that of new whorls. The results show thatAldrovanda, although usually considered as competitively weaker, can grow faster during the growing season peak thanUtricularia due to frequent branching and the subsequent rapid growth and separation of daughter shoots. Very rapid growth of rootless aquatic carnivorous plants in nutrient-poor habitats allows the consideration of ecophysiological adaptations that enable the plants to gain limiting mineral nutrients. These adaptations include carnivory, efficient nutrient reutilization from senescent shoots, and very high affinity for mineral nutrient uptake from water. Comparison of growth rates of rare and stenotopicA. vesiculosa and very common and eurytopicU. australis shows that differences in their rarity do not seem to be based on differences of growth rate.     

Experimental transmission of Leishmania tropica to hyraxes (Procavia capensis) by the bite of Phlebotomus arabicus

The ability of the sand fly Phlebotomus (Adlerius) arabicus to transmit Leishmania tropica was studied experimentally using hyraxes (Procavia capensis), natural reservoir hosts of the parasite. Sand flies became infected with L. tropica after feeding on a lesion of needle-inoculated hyrax. Moreover, P. arabicus fed with L. tropica promastigotes transmitted the parasite to hyraxes by bite during a second bloodmeal. Although the animals remained asymptomatic after infective sand fly bite, they were PCR positive and infectious for naive sand flies. We have thus demonstrated cyclical transmission of L. tropica by P. arabicus in hyraxes. This confirms experimentally the vectorial competence of P. (Adlerius) arabicus, and demonstrates that asymptomatic reservoir hosts are infectious to appropriate vectors.     

Effect of inhibition of phenylpropanoid biosynthesison peroxidase and IAA-oxidase activities and auxin contentin alfalfa suspension cultures

The inhibition of phenylpropanoid biosynthesis by 2-aminoindan-2-phosphonic acid (AIP) in alfalfa suspension cultures (Medicago sativa L.) was associated with a marked decline in the content of cinnamic acid derivatives during the whole subculture interval. The levels of all investigated forms of phenolic acids in AIP-treated cells were lower than those of control with the exception of free phenolic acids on days 1 and 2. The dynamics of free IAA content in AIP-treated cells was similar to that of the control but its peak was significantly lower. The auxin content in AIP-treated cells on days 9 and 11 represented only 35 and 40 % of control values, respectively. AIP-treatment stimulated soluble peroxidase (EC 1.11.1.7) activity in the first 2 d after cell inoculation. Time-course of soluble IAA-oxidase activities was similar to that of soluble peroxidases (with the exception of the drop in peroxidase activity on day 3) but beginning day 6, the enzyme activities in AIP-treated cells were significantly lower until the end of the subculture interval.     

Host-defense peptides from skin secretions of the tetraploid frogs Xenopus petersii and Xenopus pygmaeus, and the octoploid frog Xenopus lenduensis (Pipidae)

Peptidomic analysis of norepinephrine-stimulated skin secretions led to the identification of host-defense peptides belonging to the magainin, peptide glycine-leucine-amide (PGLa), and caerulein precursor fragment (CPF) families from the tetraploid frogs, Xenopus petersii (Peters' clawed frog) and Xenopus pygmaeus (Bouchia clawed frog), and the octoploid frog Xenopus lenduensis (Lendu Plateau clawed frog). Xenopsin-precursor fragment (XPF) peptides were not detected. The primary structures of the antimicrobial peptides from X. petersii demonstrate a close, but not conspecific relationship, with Xenopus laevis whereas the X. pygmaeus peptides show appreciable variation from previously characterized orthologs from other Xenopus species. Polyploidization events within the Xenopodinae (Silurana+Xenopus) are associated with extensive gene silencing (nonfunctionization) but unexpectedly the full complement of four PGLa paralogs were isolated from X. lenduendis secretions. Consistent with previous data, the CPF peptides showed the highest growth-inhibitory activity against bacteria with CPF-PG1 (GFGSLLGKALKIGTNLL.NH(2)) from X. pygmaeus combining high antimicrobial potency against Staphylococcus aureus (MIC=6 μM) with relatively low hemolytic activity (LC(50)=145 μM).     

Estimation of rate constants of drug binding to open channels of cardiac transient outward current

An improved approach to the evaluation of the rate constants of drugs binding to the open channel underlying the transient outward potassium current I(t0) is described. It is based on an analysis of a quantitative model formulated by a set of twelve differential equations. The rate constants are calculated from the time constants resulting from an approximation of the time course of apparent inactivation of the recorded I(t0) by two exponentials in the absence and by three exponentials in the presence of a blocking agent. The model study confirmed significantly higher accuracy in comparison with the existing electrophysiological method.     

Hho1p, the linker histone of Saccharomyces cerevisiae, is important for the proper chromatin organization in vivo

Despite the existence of certain differences between yeast and higher eukaryotic cells a considerable part of our knowledge on chromatin structure and function has been obtained by experimenting on Saccharomyces cerevisiae. One of the peculiarities of S. cerevisiae cells is the unusual and less abundant linker histone, Hho1p. Sparse is the information about Hho1p involvement in yeast higher-order chromatin organization. In an attempt to search for possible effects of Hho1p on the global organization of chromatin, we have applied Chromatin Comet Assay (ChCA) on HHO1 knock-out yeast cells. The results showed that the mutant cells exhibited highly distorted higher-order chromatin organization. Characteristically, linker histone depleted chromatin generally exhibited longer chromatin loops than the wild-type. According to the Atomic force microscopy data the wild-type chromatin appeared well organized in structures resembling quite a lot the "30-nm" fiber in contrast to HHO1 knock-out yeast.     

Haplo-insufficiency for different genes differentially reduces pathogenicity and virulence in a fungal phytopathogen

The main determinant of pathogenicity in Ustilago maydis is the b-mating locus, where establishment of heterozygosity is sufficient to cause galls/tumors on maize plants. However, matings between haploids where one partner contains a mutation, in e.g., the smu1 gene, encoding a Ste20-like PAK kinase, often show reduced mating and pathogenicity compared to wild type. Here we show that similarly, diploids lacking one copy of smu1, are reduced in production of aerial hyphae, but do not show significantly-reduced virulence. Haplo-insufficiency was also observed for additional genes. UmPde1 is a cyclic phosphodiesterase involved in cAMP turnover as part of the cAMP-dependent PKA pathway. Hsl7 plays a role in cell length and in the filamentous response to low ammonium in haploid cells. Diploids deleted for one copy of either the pde1 or hsl7 genes had reduced or increased production of aerial hyphae, respectively, and both were severely impaired in virulence compared to wild type diploids. rho1 and pdc1 are two genes essential for cell viability in haploids. These genes also displayed haplo-insufficiency for pathogenesis. rho1/Δrho1 diploid cells were defective in pheromone production and detection, aerial hyphae induction, and were avirulent. In contrast, pdc1/Δpdc1 diploid cells only failed to produce tumors when applied to maize whorls. We predict the haplo-insufficiency of most of these signaling components is due to stoichiometric imbalance of the respective gene products with their interacting partners, thereby impairing virulence-induction mechanism(s). Further investigation of the bases for such haplo-insufficiency as well as of additional genes displaying this phenotype will provide important insights into fundamental aspects of development in this organism as well as inter-nuclear communication and genetic control.     

Expression of Ccl11 associates with immune response modulation and protection against neuroinflammation in rats

Multiple sclerosis (MS) is a polygenic disease characterized by inflammation and demyelination in the central nervous system (CNS), which can be modeled in experimental autoimmune encephalomyelitis (EAE). The Eae18b locus on rat chromosome 10 has previously been linked to regulation of beta-chemokine expression and severity of EAE. Moreover, the homologous chemokine cluster in humans showed evidence of association with susceptibility to MS. We here established a congenic rat strain with Eae18b locus containing a chemokine cluster (Ccl2, Ccl7, Ccl11, Ccl12 and Ccl1) from the EAE- resistant PVG rat strain on the susceptible DA background and utilized myelin oligodendrocyte glycoprotein (MOG)-induced EAE to characterize the mechanisms underlying the genetic regulation. Congenic rats developed a milder disease compared to the susceptible DA strain, and this was reflected in decreased demyelination and in reduced recruitment of inflammatory cells to the brain. The congenic strain also showed significantly increased Ccl11 mRNA expression in draining lymph nodes and spinal cord after EAE induction. In the lymph nodes, macrophages were the main producers of CCL11, whereas macrophages and lymphocytes expressed the main CCL11 receptor, namely CCR3. Accordingly, the congenic strain also showed significantly increased Ccr3 mRNA expression in lymph nodes. In the CNS, the main producers of CCL11 were neurons, whereas CCR3 was detected on neurons and CSF producing ependymal cells. This corresponded to increased levels of CCL11 protein in the cerebrospinal fluid of the congenic rats. Increased intrathecal production of CCL11 in congenic rats was accompanied by a tighter blood brain barrier, reflected by more occludin(+) blood vessels. In addition, the congenic strain showed a reduced antigen specific response and a predominant anti-inflammatory Th2 phenotype. These results indicate novel mechanisms in the genetic regulation of neuroinflammation.