Effect of ectomycorrhizal infection on growth and photosynthetic characteristics of <Emphasis Type="Italic">Pinus densiflora</Emphasis> seedlings grown under elevated CO<Subscript>2</Subscript> concentrations

The effect of ectomycorrhizal Pisolithus tinctorius (Pt) infection was studied on the growth and photosynthetic characteristics of Pinus densiflora seedlings grown at ambient (360 µmol mol⁻¹, AC) and elevated (720 µmol mol⁻¹, EC) CO₂ concentrations. After 18 weeks, Pt inoculation had led to significantly increased dry mass and stem diameter of P. densiflora at both CO₂ concentrations, relative to non-inoculated seedlings. Moreover, EC significantly increased the ectomycorrhizal development. The phosphate content in needles inoculated with Pt was about three times higher than without inoculation at both CO₂ concentrations. The PAR saturated net photosynthetic rates (P _sat) of P. densiflora inoculated with Pt were clearly higher than for control seedlings at both CO₂ concentrations, and the maximum net photosynthetic rate (P _N) at saturated CO₂ concentration (P _max) was higher than in controls. Moreover, the carboxylation efficiency (CE) and RuBP regeneration rate of the P _N/C _i curve for P. densiflora inoculated with Pt were significantly higher than for non-inoculated seedlings at both CO₂ concentrations, especially at EC. The water use efficiency (WUE) of seedlings inoculated with Pt grown at EC was significantly raised. Allocation of photosynthates to roots was greater in Pt inoculated pine seedlings, because of the enhanced activity of ectomycorrhiza associated with seedlings at EC. Moreover, P _N of non-inoculated seedlings grown for 18 weeks at EC tended to be down regulated; in contrast, Pt inoculated seedlings showed no down-regulation at EC. The activity of ectomycorrhiza may therefore be enhanced physiological function related to water and phosphate absorption in P. densiflora seedlings at EC.This study was partly sponsored by the Ministry of Education, Sport, Culture, Science and Technology of Japan (RR2002, Basic Research B and Sprout study).     

Identification of novel mutations of the DAX-1 gene in patients with X-linked adrenal hypoplasia congenita

OBJECTIVE: X-linked adrenal hypoplasia congenita (AHC) is a condition clinically featuring adrenal insufficiency and hypogonadotropic hypogonadism caused by mutations of DAX-1. This study was undertaken to characterize the molecular defects of DAX-1 in 3 unrelated Korean patients with AHC. PATIENTS AND METHODS: Patient 1 is a 6-year-old boy who presented with a salt-losing adrenal crisis in the neonatal period. Patient 2 is a 3-year-old boy who manifested aspiration pneumonia and adrenal insufficiency at the age of 1 month. Patient 3 is a 7-year-old boy who developed an adrenal crisis at the age of 3 days. In each of these patients, DAX-1 was analyzed by direct DNA sequencing after polymerase chain reaction amplification of the entire coding region. RESULTS: Direct sequencing of DAX-1 revealed two novel mutations, 1156_1157delCT in patient 1 and another novel nonsense mutation W105X in patient 2. Patient 3 had complete deletion of DAX-1. In patient 3, serum transaminases and creatine kinase levels were elevated while the glycerol kinase activity of leukocytes was decreased. Markedly elevated glycerol excretion was detected by urine organic acid analysis. Patient 3 was diagnosed as Xp21 contiguous gene syndrome associated with deletions of the entire IL1RAPL, GK genes and the C-terminal region of DMD gene. CONCLUSIONS: Two novel mutations of DAX-1 were detected in 2 unrelated patients with AHC, and complete deletion of DAX-1 in a patient with Xp21 contiguous gene syndrome who also presented with glycerol kinase deficiency, Duchenne muscular dystrophy, and AHC.     

DNA microarrays on a dendron-modified surface improve significantly the detection of single nucleotide variations in the p53 gene

Selectivity and sensitivity in the detection of single nucleotide polymorphisms (SNPs) are among most important attributes to determine the performance of DNA microarrays. We previously reported the generation of a novel mesospaced surface prepared by applying dendron molecules on the solid surface. DNA microarrays that were fabricated on the dendron-modified surface exhibited outstanding performance for the detection of single nucleotide variation in the synthetic oligonucleotide DNA. DNA microarrays on the dendron-modified surface were subjected to the detection of single nucleotide variations in the exons 5–8 of the p53 gene in genomic DNAs from cancer cell lines. DNA microarrays on the dendron-modified surface clearly discriminated single nucleotide variations in hotspot codons with high selectivity and sensitivity. The ratio between the fluorescence intensity of perfectly matched duplexes and that of single nucleotide mismatched duplexes was >5–100 without sacrificing signal intensity. Our results showed that the outstanding performance of DNA microarrays fabricated on the dendron-modified surface is strongly related to novel properties of the dendron molecule, which has the conical structure allowing mesospacing between the capture probes. Our microarrays on the dendron-modified surface can reduce the steric hindrance not only between the solid surface and target DNA, but also among immobilized capture probes enabling the hybridization process on the surface to be very effective. Our DNA microarrays on the dendron-modified surface could be applied to various analyses that require accurate detection of SNPs.     

Genomic blueprint of Hahella chejuensis, a marine microbe producing an algicidal agent

Harmful algal blooms, caused by rapid growth and accumulation of certain microalgae in the ocean, pose considerable impacts on marine environments, aquatic industries and even public health. Here, we present the 7.2-megabase genome of the marine bacterium Hahella chejuensis including genes responsible for the biosynthesis of a pigment which has the lytic activity against a red-tide dinoflagellate. H.chejuensis is the first sequenced species in the Oceanospiralles clade, and sequence analysis revealed its distant relationship to the Pseudomonas group. The genome was well equipped with genes for basic metabolic capabilities and contained a large number of genes involved in regulation or transport as well as with characteristics as a marine heterotroph. Sequence analysis also revealed a multitude of genes of functional equivalence or of possible foreign origin. Functions encoded in the genomic islands include biosynthesis of exopolysacchrides, toxins, polyketides or non-ribosomal peptides, iron utilization, motility, type III protein secretion and pigmentation. Molecular structure of the algicidal pigment, which was determined through LC-ESI-MS/MS and NMR analyses, indicated that it is prodigiosin. In conclusion, our work provides new insights into mitigating algal blooms in addition to genetic make-up, physiology, biotic interactions and biological roles in the community of a marine bacterium.     

Scoring schemes of palindrome clusters for more sensitive prediction of replication origins in herpesviruses

Many empirical studies show that there are unusual clusters of palindromes, closely spaced direct and inverted repeats around the replication origins of herpesviruses. In this paper, we introduce two new scoring schemes to quantify the spatial abundance of palindromes in a genomic sequence. Based on these scoring schemes, a computational method to predict the locations of replication origins is developed. When our predictions are compared with 39 known or annotated replication origins in 19 herpesviruses, close to 80% of the replication origins are located within 2% of the genome length. A list of predicted locations of replication origins in all the known herpesviruses with complete genome sequences is reported.     

Sepiapterin reductases from Chlorobium tepidum and Chlorobium limicola catalyze the synthesis of L-threo-tetrahydrobiopterin from 6-pyruvoyltetrahydropterin

The ORF sequences of the gene encoding sepiapterin reductase were cloned from the genomic DNAs of Chlorobium tepidum and Chlorobium limicola, which are known to produce L-threo- and L-erythro-tetrahydrobiopterin (BH4)-N-acetylglucosamine, respectively. The deduced amino acid sequence of C. limicola consists of 241 residues, while C. tepidum SR has three residues more at the C-terminal. The overall protein sequence identity was 87.7%. Both recombinant proteins generated from Escherichia coli were identified to catalyze reduction of diketo compound 6-pyruvoyltetrahydropterin to L-threo-BH4. This result suggests that C. limicola needs an additional enzyme for L-erythro-BH4 synthesis to yield its glycoside. The catalytic activity of Chlorobium SRs also supports the previously proposed mechanism of two consecutive reductions of C1' carbonyl group of 6-pyruvoyltetrahydropterin via isomerization reaction.     

Inhibition of thrombin-induced microglial activation and NADPH oxidase by minocycline protects dopaminergic neurons in the substantia nigra in vivo

The present study shows that activation of microglial NADPH oxidase and production of reactive oxygen species (ROS) is associated with thrombin-induced degeneration of nigral dopaminergic neurons in vivo. Seven days after thrombin injection in the rat substantia nigra (SN), tyrosine hydroxylase immunocytochemistry showed a significant loss of nigral dopaminergic neurons. This cell death was accompanied by localization of terminal deoxynucleotidyl transferase-mediated fluorecein UTP nick-end labelling (TUNEL) staining within dopaminergic neurons. This neurotoxicity was antagonized by the semisynthetic tetracycline derivative, minocycline, and the observed neuroprotective effects were associated with the ability of minocycline to suppress NADPH oxidase-derived ROS production and pro-inflammatory cytokine expression, including interleukin-1beta and inducible nitric oxide synthase, from activated microglia. These results suggest that microglial NADPH oxidase may be a viable target for neuroprotection against oxidative damage.