Reexamination of sectional classification in far easternEuphorbia subgenusEsula (Euphorbiaceae) using morphological and phenolic data

Reexamining the classification proposed by Hurusawa, the phylogeny of Far EasternEuphorbia subgenusEsula was analyzed using thirteen morphological and seventeen phenolic compound data. These data were analyzed independently and in combination using PAUP under the assumptions of Fitch parsimony. Ten species, comprised of three sections and five subsections within Far EasternEuphorbia subg.Esula and one outgroup from subg.Chamaesyce, were used as terminal taxa. The phylogenetic results did not support the sectional classifications within subg.Esula proposed by Hurusawa. SectionDecussatae was nested in the paraphyletic sectEsula in all of the analyses, and the relationship of sectHelioscopiae was equivocal among data sets. The disagreement of data sets over the placement ofEuphorbia ebracteolata is probably due to a hybrid origin of the species and missing phenolic data forE. pallasii. A sister-group relationship of the Korean endemicE. fauriei with the widespreadE. pekinensis was strongly supported by the morphological and phenolic data.     

Phase properties of liquid-crystalline Phosphatidylcholine/Phosphatidylethanolamine bilayers revealed by fluorescent probes.

The mixing properties of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) were examined in liquid-crystalline phase using fluorescent probes incorporated into lipid bilayers. The excimer to monomer (E/M) fluorescence ratio of 1-hexadecanoyl-2-(1-pyrenedecanoyl)-sn-glycero-3-phosphocholine (PPC) versus PPC concentration was higher for binary mixtures containing phosphatidylcholine (PC)/phosphatidylethanolamine (PE) (1:1) compared to PC matrix. When POPC was gradually replaced with POPE, the E/M ratio also increased suggesting the enhanced lateral mobility or the lateral enrichment of PPC into domains or both. Evidences for the PE-induced domain formation were further provided by resonance energy transfer between 2-(4, 4-difluoro-5-methyl-4-boro-3a, 4a-diaza-s-indacene-3-dodecanoyl)-1-hexadecanoyl-sn-glycero- 3-phospho choline and PPC, which was enhanced as a function of PE concentration, and by the polarization of 1,6-diphenyl-1,3, 5-hexatriene. In addition, PE reduced free volume and polarity of lipid bilayers as measured by the emission fluorescence of 1,2-bis PPC and 6-lauroyl-2-dimethylaminonaphthalene. When POPE analogs with a methylated head group instead of normal POPE were used, the diminished effect on the domain formation was shown in the order N-methyl PE > N,N-dimethyl PE. The results suggest that the mixing properties of POPE and POPC are not random but that lipid domains of phospholipids are formed.     

Inhibition of Mitogen-Activated Kinase Signaling Sensitizes HeLa Cells to Fas Receptor-Mediated Apoptosis

The Fas receptor (FasR) is an important physiological mediator of apoptosis in various tissues and cells. However, there are also many FasR-expressing cell types that are normally resistant to apoptotic signaling through this receptor. The mitogen-activated protein kinase (MAPK) signaling cascade has, apart from being a growth-stimulating factor, lately received attention as an inhibitory factor in apoptosis. In this study, we examined whether MAPK signaling could be involved in protecting FasR-insensitive cells. To this end, we used different approaches to inhibit MAPK signaling in HeLa cells, including treatment with the MAPK kinase inhibitor PD 98059, serum withdrawal, and expression of dominant-interfering MAPK kinase mutant protein. All of these treatments were effective in sensitizing the cells to FasR-induced apoptosis, demonstrating that MAPK indeed is involved in the control of FasR responses. The MAPK-mediated control seemed to occur at or upstream of caspase 8, the initiator caspase in apoptotic FasR responses. Transfection with the constitutively active MAPK kinase abrogated FasR-induced apoptosis also in the presence of cycloheximide, indicating that the MAPK-generated suppression of FasR-mediated apoptotic signaling is protein synthesis independent. In cells insensitive to FasR-induced apoptosis, stimulation of the FasR with an agonistic antibody resulted in significant MAPK activation, which was inhibited by PD 98059. When different cell types were compared, the FasR-mediated MAPK activation seemed proportional to the degree of FasR insensitivity. These results suggest that the FasR insensitivity is likely to be a consequence of FasR-induced MAPK activation, which in turn interferes with caspase activation.     

Molecular interactions in ribose transport: the binding protein module symmetrically associates with the homodimeric membrane transporter.

The Escherichia coli high-affinity ribose transporter is composed of the periplasmic ribose-binding protein (RBP or RbsB), the membrane component (RbsC) and the ATP-binding protein (RbsA). In order to dissect the molecular interactions initiating the transport process, RbsC suppressors for transport-defective rbsB mutations were isolated. These suppressors are localized in two regions of RbsC, which are allele-specific to N- or C-terminal domain mutations of RBP, suggesting that there are two distinct regions of RbsC, each interacting with one of the two domains of RBP. To demonstrate that these two regions provide a homodimeric binding surface for RBP we constructed a dimeric rbsC in which two genes are joined tandemly from head to tail with the addition of a linker. The dimeric RbsC protein is stable and functional in growth and ribose uptake. By exploiting the allele specificity between the domain-specific mutations and their suppressors, we generated all mutation-suppressor combinations in a single rbsB plus the dimeric rbsC genes. Their phenotypes are consistent with the proposal that the binding protein module interacts symmetrically with homodimeric RbsC. The mode of association proposed here for the ribose transport components could be extended to other ABC transporters with similar structural organizations.     

Identification of the genes encoding enzymes involved in the early biosynthetic pathway of pteridines in Synechocystis sp. PCC 6803

The biosynthetic pathway for the pteridine moiety of cyanopterine, as well as tetrahydrobiopterine, has been investigated in Synechocystis sp. PCC 6803. Open reading frames slr0426, slr1626, slr0078 and sll0330 of the organism putatively encoding GTP cyclohydrolase I, dihydroneopterine aldolase, 6-pyruvoyltetrahydropterine synthase and sepiapterine reductase, respectively, have been cloned into T7-based vectors for expression in Escherichia coli. The recombinant proteins have been purified to homogeneity and demonstrated to possess expected genuine activities except that of sll0330. Our result is the first direct evidence for the functional assignment of the open reading frames in Synechocystis sp. PCC 6803. Furthermore, the 6-pyruvoyltetrahydropterine synthase gene is demonstrated for the first time in prokaryotes. Based on the result, biosynthesis of cyanopterine is discussed.     

Antioxidative and Proapoptotic Effects of Riluzole on Cultured Cortical Neurons

Abstract : Riluzole is used clinically in patients with amyotrophic lateral sclerosis. As oxidative stress, in addition to excitotoxicity, may be a major mechanism of motoneuron degeneration in patients with amyotrophic lateral sclerosis, we examined whether riluzole protects against nonexcitotoxic oxidative injury. Probably reflecting its weak antiexcitotoxic effects, riluzole (1-30 μ M ) attenuated submaximal neuronal death induced by 24-h exposure to 30 μ M kainate or NMDA, but not that by 100 μ M NMDA, in cortical cultures. Riluzole also attenuated nonexcitotoxic oxidative injury induced by exposure to FeCl₃ in the presence of MK-801 and CNQX. Consistent with its antioxidative effects, riluzole reduced Fe³⁺-induced lipid peroxidation, and inhibited cytosolic phospholipase A₂. By contrast, riluzole did not attenuate neuronal apoptosis induced by staurosporine. Rather unexpectedly, 24-48-h exposure to 100-300 μ M riluzole induced neuronal death accompanied by nuclear and DNA fragmentations, which was attenuated by caspase inhibitor carbobenzyloxy-Val-Ala-Asp-fluoromethyl ketone but not by protein synthesis inhibitor cycloheximide. The present study demonstrates that riluzole has direct antioxidative actions, perhaps in part by inhibiting phospholipase A₂. However, in the same neurons, riluzole paradoxically induces neuronal apoptosis in a caspase-sensitive manner. Considering current clinical use of riluzole, further studies are warranted to investigate its potential cytolethal effects.     

Pseudomonas syringae effector HopZ3 suppresses the bacterial AvrPto1–tomato PTO immune complex via acetylation

The plant pathogen Pseudomonas syringae secretes multiple effectors that modulate plant defenses. Some effectors trigger defenses due to specific recognition by plant immune complexes, whereas others can suppress the resulting immune responses. The HopZ3 effector of P. syringae pv. syringae B728a (PsyB728a) is an acetyltransferase that modifies not only components of plant immune complexes, but also the Psy effectors that activate these complexes. In Arabidopsis, HopZ3 acetylates the host RPM1 complex and the Psy effectors AvrRpm1 and AvrB3. This study focuses on the role of HopZ3 during tomato infection. In Psy-resistant tomato, the main immune complex includes PRF and PTO, a RIPK-family kinase that recognizes the AvrPto effector. HopZ3 acts as a virulence factor on tomato by suppressing AvrPto1_Psy-triggered immunity. HopZ3 acetylates AvrPto1_Psy and the host proteins PTO, SlRIPK and SlRIN4s. Biochemical reconstruction and site-directed mutagenesis experiments suggest that acetylation acts in multiple ways to suppress immune signaling in tomato. First, acetylation disrupts the critical AvrPto1_Psy-PTO interaction needed to initiate the immune response. Unmodified residues at the binding interface of both proteins and at other residues needed for binding are acetylated. Second, acetylation occurs at residues important for AvrPto1_Psy function but not for binding to PTO. Finally, acetylation reduces specific phosphorylations needed for promoting the immune-inducing activity of HopZ3’s targets such as AvrPto1_Psy and PTO. In some cases, acetylation competes with phosphorylation. HopZ3-mediated acetylation suppresses the kinase activity of SlRIPK and the phosphorylation of its SlRIN4 substrate previously implicated in PTO-signaling. Thus, HopZ3 disrupts the functions of multiple immune components and the effectors that trigger them, leading to increased susceptibility to infection. Finally, mass spectrometry used to map specific acetylated residues confirmed HopZ3’s unusual capacity to modify histidine in addition to serine, threonine and lysine residues.     

Application of the Maryblyt Model for the Infection of Fire Blight on Apple Trees at Chungju,Jecheon, and Eumsung during 2015–2020

To preventively control fire blight in apple trees and determine policies regarding field monitoring, the Maryblyt ver. 7.1 model (MARYBLYT) was evaluated in the cities of Chungju, Jecheon, and Eumseong in Korea from 2015 to 2020. The number of blossom infection alerts was the highest in 2020 and the lowest in 2017 and 2018. And the common feature of MARYBLYT blossom infection risks during the flowering period was that the time of BIR-High or BIR-Infection alerts was the same regardless of location. The flowering periods of the trees required to operate the model varied according to the year and geographic location. The model predicts the risk of “Infection” during the flowering periods, and recommends the appropriate times to control blossom infection. In 2020, when flower blight was severe, the difference between the expected date of blossom blight symptoms presented by MARYBLYT and the date of actual symptom detection was only 1–3 days, implying that MARYBLYT is highly accurate. As the model was originally developed based on data obtained from the eastern region of the United States, which has a climate similar to that of Korea, this model can be used in Korea. To improve field utilization, however, the entire flowering period of multiple apple varieties needs to be considered when the model is applied. MARYBLYT is believed to be a useful tool for determining when to control and monitor apple cultivation areas that suffer from serious fire blight problems.     

Extermination Speed of an Imidacloprid and Flumethrin Polymer Matrix Collar against Larvae,Nymphs and Adults of Haemaphysalis longicornis

The objective of this study was to evaluate the efficacy of an imidacloprid 10% and flumethrin 4.5% polymer matrix collar against the developmental stages of Haemaphysalis longicornis infesting dogs using the hair from treated dogs in a semi-in-vitro assay set. When incubated with 0.5 g of the hair collected from the dogs installed with the drug-embedded collar after 10 days, average death rate of the larval, nymphal, and adult H. longicornis was 21.5%, 77.9%, and 100% at 30 min, 1 hr, and 2 hr, respectively. This study showed the larval stages as well as the nymphal and adult stages of H. longicornis ticks are killed upon contact with the hair from dogs treated with the collar within 2 hr.