Golgi/plastid‐type manganese superoxide dismutase involved in heat‐stress tolerance during grain filling of rice

Superoxide dismutase (SOD) is widely assumed to play a role in the detoxification of reactive oxygen species caused by environmental stresses. We found a characteristic expression of manganese SOD 1 (MSD1) in a heat‐stress‐tolerant cultivar of rice (Oryza sativa). The deduced amino acid sequence contains a signal sequence and an N‐glycosylation site. Confocal imaging analysis of rice and onion cells transiently expressing MSD1‐YFP showed MSD1‐YFP in the Golgi apparatus and plastids, indicating that MSD1 is a unique Golgi/plastid‐type SOD. To evaluate the involvement of MSD1 in heat‐stress tolerance, we generated transgenic rice plants with either constitutive high expression or suppression of MSD1. The grain quality of rice with constitutive high expression of MSD1 grown at 33/28 °C, 12/12 h, was significantly better than that of the wild type. In contrast, MSD1‐knock‐down rice was markedly susceptible to heat stress. Quantitative shotgun proteomic analysis indicated that the overexpression of MSD1 up‐regulated reactive oxygen scavenging, chaperone and quality control systems in rice grains under heat stress. We propose that the Golgi/plastid MSD1 plays an important role in adaptation to heat stress.     

CLUMSY VEIN,the Arabidopsis DEAH‐box Prp16 ortholog,is required for auxin‐mediated development

Pre‐messenger RNA (pre‐mRNA) splicing is essential in eukaryotic cells. In animals and yeasts, the DEAH‐box RNA‐dependent ATPase Prp16 mediates conformational change of the spliceosome, thereby facilitating pre‐mRNA splicing. In yeasts, Prp16 also plays an important role in splicing fidelity. Conversely, PRP16 orthologs in Chlamydomonas reinhardtii and nematode do not have an important role in general pre‐mRNA splicing, but are required for gene silencing and sex determination, respectively. Functions of PRP16 orthologs in higher plants have not been described until now. Here we show that the CLUMSY VEIN (CUV) gene encoding the unique Prp16 ortholog in Arabidopsis thaliana facilitates auxin‐mediated development including male‐gametophyte transmission, apical–basal patterning of embryonic and gynoecium development, stamen development, phyllotactic flower positioning, and vascular development. cuv‐1 mutation differentially affects splicing and expression of genes involved in auxin biosynthesis, polar auxin transport, auxin perception and auxin signaling. The cuv‐1 mutation does not have an equal influence on pre‐mRNA substrates. We propose that Arabidopsis PRP16/CUV differentially facilitates expression of genes, which include genes involved in auxin biosynthesis, transport, perception and signaling, thereby collectively influencing auxin‐mediated development.     

Prevalence and characterization of Chlamydia DNA in zoo animals in Japan

Because many people visit zoos, prevention of zoonoses is important from the standpoint of public health. This study examined the prevalence of Chlamydia among zoo animals in Japan by PCR and characterized these bacteria by performing phylogenetic analyses of the sequences of the variable domain (VD) 2 and VD4 regions of the ompA gene, which encodes the Chlamydia major outer membrane protein. Fecal samples were collected from 1150 zoo animals in five zoos and examined for Chlamydia DNA. Chlamydia psittaci DNA was found in 3.9% of mammals, 7.2% of birds and 8.1% of reptiles. The prevalence of Chlamydia pneumoniae DNA was significantly higher in reptiles (5.8%) than in mammals (0.3%) and birds (0.3%). Phylogenetic analysis of the ompA VD2 region from 18 samples showed that nine were in three different clusters containing C. psittaci strains, six were in a cluster containing C. pneumoniae strains and three each formed a distinct branch. Furthermore, phylogenetic analysis of the ompA VD4 region showed that C. pneumoniae DNAs from reptiles were close to those from human patients. The C. pneumoniae DNAs from the European glass lizard, Emerald tree boa, and Panther chameleon were classified in clusters that were distinct from other strains, suggesting that these reptiles had each been infected with a specific C. pneumoniae genotype. This study showed that diverse Chlamydia strains have been prevalent among a variety of zoo animals.     

Differential contributions of plant Dicer‐like proteins to antiviral defences against potato virus X in leaves and roots

Members of the plant Dicer‐like (DCL) protein family are the critical components of the RNA‐silencing pathway that mediates innate antiviral defence. The distinct antiviral role of each individual DCL protein has been established with mostly based on observations of aerial parts of plants. Thus, although the roots are closely associated with the life cycle of many plant viruses, little is known about the antiviral activities of DCL proteins in roots. We observed that antiviral silencing strongly inhibits potato virus X (PVX) replication in roots of some susceptible Solanaceae species. Silencing of the DCL4 homolog in Nicotiana benthamiana partially elevated PVX replication levels in roots. In Arabidopsis thaliana, which was originally considered a non‐host plant of PVX, high levels of PVX accumulation in inoculated leaves were achieved by inactivation of DCL4, while in the upper leaves and roots, it required the additional inactivation of DCL2. In transgenic A. thaliana carrying the PVX amplicon with a green fluorescent protein (GFP) gene insertion in the chromosome (AMP243 line), absence of DCL4 enabled high levels of PVX‐GFP accumulation in various aerial organs but not in the roots, suggesting that DCL4 is critical for intracellular antiviral silencing in shoots but not in roots, where it can be functionally compensated by other DCL proteins. Together, the high level of functional redundancies among DCL proteins may contribute to the potent antiviral activities against PVX replication in roots.     

Poly(L-Lysine)-Graft-Dextran Copolymer Remarkably Promotes Pyrimidine-Motif Triplex Formation at Neutral Ph: Thermodynamic and Kinetic Studies

Abstract

The binding constant of a homopyrimidine oligonucleotide with its target duplex for the pyrimidine-motif triplex formation at neutral pH was analyzed and found to be remarkably higher in the presence of the poly (L-lysine)-graft-dextran copolymer than that without any triplex stabilizer or in the presence of spermine. The promoting effect mainly results from the considerable increase in the association rate constant.     

Synthesis and Anti-HIV Activity of 6-Substituted Purine 2′-Deoxy-2′-fluororibosides

Abstract

3′,5′-Di-O-protected 6-chloropurine arabinoside 4b was treated with diethylaminosulfur trifluoride (DAST) and subsequently deprotected with pyridinium p-toluenesulfonate to give 6-chloropurine 2′-deoxy-2′-fluororiboside 6a. The displacement with nucleophile afforded the 6-substituted congener 6b-e. Treatment of 5′-O-protected 6-chloropurine arabinoside 3c with DAST gave lyxoepoxide 7.     

Comparative Studies of the Thermodynamic Stabilities Between Sheared A:G and Watson-Crick A:U(T) Base Pairs in RNA and DNA

Abstract

Thermodynamic parameters for duplex formation were determined from CD melting curves for r(GGACGAGUCC)₂ and d(GGACGAGTCC)₂, both of which form two consecutive ‘sheared’ A:G base pairs at the center [Katahira et al. (1993) Nucleic Acids Res. 21, 5418–5424; Katahira et al., (1994) Nucleic Acids Res. 22, 2752–27591. The parameters were determined also for r(GGACUAGUCC)₂ and d(GGACTAGTCC)₂, where the A:G mismatches are replaced by Watson-Crick A:U(T) base pairs. Thermodynamic properties for duplex formation are compared between the sheared and the Watson-Crick base pairs, and between RNA and DNA. Difference in the thermodynamic stability is analyzed and discussed in terms of enthalpy and entropy changes. The characteristic features in CD spectra of RNA and DNA containing the sheared A:G base pairs are also reported.

     

Synthesis of 6-Arylthio Analogs of 2′,3′-Dideoxy-3′-Fluoroguanosine and Their Effect against Hepatitis B Virus Replication

A key compound, 2-amino-6-chloro-9-(2,3-dideoxy-3-fluoro-β-D-erythro-pentofuranosyl)purine, was prepared from 2-amino-6-chloropurine riboside in 5 steps, then subjected to the nucleophilic displacement with benzenethiols to afford 6-arylthio congeners. These compounds showed a similar anti-HBV effect to that of 2′,3′-dideoxy-3′-fluoroguanosine.     

Canopy‐scale relationships between stomatal conductance and photosynthesis in irrigated rice

Modeling stomatal behavior is critical in research on land–atmosphere interactions and climate change. The most common model uses an existing relationship between photosynthesis and stomatal conductance. However, its parameters have been determined using infrequent and leaf‐scale gas‐exchange measurements and may not be representative of the whole canopy in time and space. In this study, we used a top‐down approach based on a double‐source canopy model and eddy flux measurements throughout the growing season. Using this approach, we quantified the canopy‐scale relationship between gross photosynthesis and stomatal conductance for 3 years and their relationships with leaf nitrogen content throughout each growing season above a paddy rice canopy in Japan. The canopy‐averaged stomatal conductance (g_sc) increased with increasing gross photosynthesis per unit green leaf area (A_g), as was the case with leaf‐scale measurements, and 41–90% of its variation was explained by variations in A_g adjusted to account for the leaf‐to‐air vapor‐pressure deficit and CO₂ concentration using the Leuning model. The slope (m) in this model (g_sc versus the adjusted A_g) was almost constant within a 15‐day period, but changed seasonally. The m values determined using an ensemble dataset for two mid‐growing‐season 15‐day periods were 30.8 (SE = 0.5), 29.9 (SE = 0.7), and 29.9 (SE = 0.6) in 2004, 2005, and 2006, respectively; the overall mid‐season value was 30.3 and did not greatly differ among the 3 years. However, m appeared to be higher during the early and late growing seasons. The ontogenic changes in leaf nitrogen content strongly affected A_g and thus g_sc. In addition, we have discussed the agronomic impacts of the interactions between leaf nitrogen content and g_sc. Despite limitations in the observations and modeling, our canopy‐scale results emphasize the importance of continuous, season‐long estimates of stomatal model parameters for crops using top‐down approaches.     

Efficacy and safety of paromomycin for treating amebiasis in Japan

The clinical management of amebiasis is a growing concern, particularly among human immunodeficiency virus (HIV)-infected individuals who are predisposed to severe illness. Treatment with a luminal amebicide is strongly recommended following acute-stage treatment with a nitroimidazole. In 2004, the Japanese Research Group on Chemotherapy of Tropical Diseases introduced paromomycin, which was not nationally licensed, and offered it to a number of patients. From 2004 to 2011, 143 case records of amebiasis (123 with amebic colitis, 16 with amebic liver abscess, and 4 with both) in which patients were treated with paromomycin, mainly 1500 mg/day for 9 or 10 days following metronidazole treatment, were submitted. Among 123 evaluable cases, 23 (18.7%) experienced possible adverse effects, the most common being diarrhea (17/123, 13.8%) and other gastrointestinal problems that were resolved after the completion or discontinuation of treatment. In addition, single cases of bloody stools associated with Clostridium difficile colitis, skin rash, and the elevation of liver enzymes were also reported, although the causal relationship was not clear. HIV infection did not appear to increase the incidence of adverse drug effects. Each of the 11 asymptomatic or mildly symptomatic amebic colitis cases became negative for stool cysts after paromomycin treatment. Paromomycin was shown to be safe and well tolerated, as well as effective in a special subset of amebic colitis cases.