Role of 2',5'-oligo(adenylic acid) polymerase in the degradation of ribonucleic acid linked to double-stranded ribonucleic acid by extracts of interferon-treated cells

RNA covalently linked to double-stranded RNA (dsRNA) is preferentially degraded in extracts of interferon-treated HeLa cells [Nilsen, T. W., & Baglioni, C. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 2600-2604]. The size of the dsRNA required for this preferential degradation has been determined by annealing poly(I) of known length to the poly(C) tract of encephalomyocarditis virus (EMCV) RNA or by annealing poly(U) to poly(A) of known length of vesicular stomatitis virus mRNA. The dsRNA must be longer than about 60 base pairs to observe the preferential degradation of RNA. Moreover, triple-stranded regions that do not activate synthesis of 2',5'-oligo(A) and ethidium bromide, which intercalates in dsRNA and blocks 2',5'-olido(A) polymerase activation, prevent this degradation. Ethidium also blocks the degradation of the replicative intermediate of EMCV by extracts of interferon-treated cells. These experiments indicate that synthesis of 2',5'-oligo(A) is required for the degradation of RNA linked to dsRNA. The 2',5'-oligo(A)-dependent endonuclease does not cleave single- or double-stranded DNA, nor does it cleave homopolyribonucleotides. The potential role of the 2',5'-oligo(A) polymerase/endonuclease system in the inhibition of viral RNA replication is discussed.     

Effect of nitrogen on drought strain and nutrient uptake in Norway spruce Picea abies (L.) Karst.) trees

A field lysimeter study was established with the aim of investigating the effect of nitrogen availability upon drought strain in Norway spruce trees. Forest soil (Typic Udipsamment) was filled in lysimeters 1 m in diameter and 1 m deep. Small trees of Norway spruce from five different clones were planted in the lysimeters. Roofs under the canopy of the trees ensured full control of water and nutrient input. Three levels of nitrogen were given to the trees during five years; ambient rainwater, and five and fifteen times this N concentration, respectively. Additional N was given as NH₄NO₃ in irrigation water. Mean annual N-addition during the five years corresponded to 5, 27 and 82 kg per ha and year for the three treatments, respectively. During the third and fifth growth season drought was artificially induced. In addition to a watered control, two levels of drought were applied, representing water deprivation for 2 and 3 months, respectively, in 1990 and 3 and 4 months, respectively in 1992. A higher water consumption in the nitrogen fertilized trees during the droughts resulted in a significantly lower pre-dawn shoot water potential compared to the trees receiving ambient rain N. The interaction between drought and nitrogen fertilization was clear also for photosynthesis and transpiration. A decrease in height- and diameter increment caused by drought was most pronounced in the 82 kg N ha^–1 yr^–1 treatment. A water strain integral showed a strong positive correlation to the needle biomass of the trees. Foliar concentrations of several nutrients decreased significantly with increasing drought strain in the trees. Concentration of potassium and boron were especially low and visual symptoms of deficiency occurred.     

Systematic identification and characterization of stress-inducible heat shock proteins (HSPs) in the salmon louse (<Emphasis Type="Italic">Lepeophtheirus salmonis</Emphasis>)

Salmon lice (Lepeophtheirus salmonis) are parasitic copepods, living mainly on Atlantic salmon and leading to large economical losses in aquaculture every year. Due to the emergence of resistances to several drugs, alternative treatments are developed, including treatment with hydrogen peroxide, freshwater or thermal treatment. The present study gives a first overview of the thermotolerance and stress response of salmon lice. Sea lice nauplii acclimated to 10 °C can survive heat shocks up to 30 °C and are capable of hardening by a sublethal heat shock. We searched in the genome for heat shock protein (HSP) encoding genes and tested their inducibility after heat shock, changes in salinity and treatment with hydrogen peroxide, employing microfluidic qPCRs. We assessed 38 candidate genes, belonging to the small HSP, HSP40, HSP70 and HSP90 families. Nine of these genes showed strong induction after a non-lethal heat shock. In contrast, only three and two of these genes were induced after changes in salinity and incubation in hydrogen peroxide, respectively. This work provides the basis for further work on the stress response on the economically important parasite L. salmonis.     

The trade-off between molt and parental care: a sexual conflict in the blue tit?

Breeding activities and molt are generally thought to be mutuallyexclusive in birds since both are energetically costly and arenormally separated in time. However, sometimes molt overlapswith breeding to some degree. A trade-off between adult somaticmaintenance functions (feather renewal) and parental care isthen to be expected. The consequences of this are largely unknown,and there are few studies that have shown any fitness costsof molt-breeding overlap. We investigated the consequences ofmolt-breeding overlap by removing first clutches of blue titParus casruleus pairs, thereby inducing late repeat clutches.Among the delayed pairs, a high proportion of males and somefemales started their molt already during incubation or nestlingfeeding. Molting males fed their nestlings to a lesser extentthan non-molting ones, and nestling mortality increased as adirect result of the early timing of male molt. Furthermore,the ability to raise an experimentally enlarged brood was negativelycoupled to the molt stage of the male. Our data thus provideevidence that molt-breeding overlap leads to fitness costs,and we discuss the results within the context of sexual conflictand the implications for optimization of avian reproductivedecisions     

Functional and structural consequences of aromatic residue substitutions within the kringle-2 domain of tissue-type plasminogen activator.

Aromatic amino acid residues within kringle domains play important roles in the structural stability and ligand-binding properties of these protein modules. In previous investigations, it has been demonstrated that the rigidly conserved Trp25 is primarily involved in stabilizing the conformation of the kringle-2 domain of tissue-type plasminogen activator (K2tpA), whereas Trp63, Trp74, and Tyr76 function in omega-amino acid ligand binding, and, to varying extents, in stabilizing the native folding of this kringle module. In the current study, the remaining aromatic residues of K2tPA, viz., Tyr2, Phe3, Tyr9, Tyr35, Tyr52, have been subjected to structure-function analysis via site-directed mutagenesis studies. Ligand binding was not significantly influenced by conservative amino acid mutations at these residues, but a radical mutation at Tyr35 destabilized the interaction of the ligand with the variant kringle. In addition, as reflected in the values of the melting temperatures, changes at Tyr9 and Tyr52 generally destabilized the native structure of K2tPA to a greater extent than changes at Tyr2, Phe3, and Tyr35. Taken together, results to date show that, in concert with predictions from the crystal structure of K2tpA, ligand binding appears to rely most on the integrity of Trp63 and Trp74, and aromaticity at Tyr76. With regard to aromatic amino acids, kringle folding is most dependent on Tyr9, Trp25, Tyr52, Trp63, and Tyr76. As yet, no obvious major roles have been uncovered for Tyr2, Phe3, or Tyr35 in K2tpA.     

Estrogen‐regulated developmental neuronal apoptosis is determined by estrogen receptor subtype and the Fas/Fas ligand system

Adult sexual dimorphism in neuronal cell number is controlled by estrogen exposure during a tightly defined period of rat brain development. The mechanisms of estrogen's effect are unknown; one possibility is regulation of programmed cell death (apoptosis). In this study we have shown that estradiol can function as a neuroprotective agent or an inducer of apoptosis, depending on the estrogen receptor‐subtype present in the cell. Thus, ERα has a neuroprotective effect, while ERβ mediates the induction of apoptosis in neuronal cells. Moreover, we show that estrogen‐induced apoptosis through ER‐β requires the expression of Fas‐ and Fas ligand (FasL) proteins, since the absence of FasL in neurons prevents this effect. Furthermore, we demonstrate that microglia‐secreted products induce the expression of FasL necessary to mediate estradiol–ERβ apoptotic effect. These findings may explain the dichotomous effect of fetal estradiol on the adult neuronal number. © 2000 John Wiley & Sons, Inc. J Neurobiol 43: 64–78, 2000     

A trypsin-like protease with apparent dual function in early Lepeophtheirus salmonis (Kr?yer) development

Background  

Trypsin-like serine proteases are involved in a large number of processes including digestive degradation, regulation of developmental processes, yolk degradation and yolk degradome activation. Trypsin like peptidases considered to be involved in digestion have been characterized in Lepeophtheirus salmonis. During these studies a trypsin-like peptidase which differed in a number of traits were identified.     

Mice lacking Alkbh1 display sex-ratio distortion and unilateral eye defects

Background

Eschericia coli AlkB is a 2-oxoglutarate- and iron-dependent dioxygenase that reverses alkylated DNA damage by oxidative demethylation. Mouse AlkB homolog 1 (Alkbh1) is one of eight members of the newly discovered family of mammalian dioxygenases.

Methods and Findings

In the present study we show non-Mendelian inheritance of the Alkbh1 targeted allele in mice. Both Alkbh1^−/− and heterozygous Alkbh1^+/− offspring are born at a greatly reduced frequency. Additionally, the sex-ratio is considerably skewed against female offspring, with one female born for every three to four males. Most mechanisms that cause segregation distortion, act in the male gametes and affect male fertility. The skewing of the sexes appears to be of paternal origin, and might be set in the pachythene stage of meiosis during spermatogenesis, in which Alkbh1 is upregulated more than 10-fold. In testes, apoptotic spermatids were revealed in 5–10% of the tubules in Alkbh1^−/− adults. The deficiency of Alkbh1 also causes misexpression of Bmp2, 4 and 7 at E11.5 during embryonic development. This is consistent with the incompletely penetrant phenotypes observed, particularly recurrent unilateral eye defects and craniofacial malformations.

Conclusions

Genetic and phenotypic assessment suggests that Alkbh1 mediates gene regulation in spermatogenesis, and that Alkbh1 is essential for normal sex-ratio distribution and embryonic development in mice.