Physical and gene maps of the unicellular cyanobacterium Synechococcus sp. strain PCC6301 genome

A physical map of the unicellular cyanobacterium Synechococcus sp. strain PCC6301 genome has been constructed with restriction endonucleases PmeI, SwaI, and an intron-encoded endonuclease I-CeuI. The estimated size of the genome is 2.7 Mb. On the genome 49 genes or operons have been mapped. Two rRNA operons are separated by 600 kb and transcribed oppositely.     

Spectroscopic and electrical properties of the [W(C3Se5)3] anion complex (C3Se5 = 1,3-diselenole-2-selone-4,5-diselenolate) and the oxidized species

[NBuⁿ₄]₂[W(C₃Se₅)₃] (C₃Se₅²⁻ = 1,3-diselenole-2-selone-4,5- diselenolate(2−)) was prepared by the reaction of Na₂[C₃Se₅] with WCl₆ in ethanol, followed by addition of [NBuⁿ₄]Br. The cyclic voltammogram in dichloromethane exhibits two oxidation peaks at −0.04 and +0.03 V (versus SCE). The complex reacted with [Fe(C₅Me₅)₂][BF₄], iodine or [TTF]₃[BF₄]₂ (TTF^·+ = the tetrathiafulvalenium radical cation) in acetonitrile to afford the oxidized complexes [Fe(C₅Me₅)₂]_0.5[W(C₃Se₅)₃], [NBuⁿ₄]_0.1[W(C₃Se₅)₃] and [TTF]_0.5[W(C₃Se₅)₃], respectively. Current-controlled electrochemical oxidation of the complex in acetonitrile gave [NBuⁿ₄]_0.6[W(C₃Se₅)₃]. The oxidized complexes exhibit electrical conductivities of 4.7×10 ⁻⁵−1.5×10⁻³ S cm⁻¹ at room temperature measured for compacted pellets. Electronic absorption, IR and ESR spectra of these complexes are discussed.     

Genes Encoding the Group I Intron-containing tRNALeu and Subunit L of NADH Dehydrogenase from the Cyanobacterium Synechococcus PCC 6301

A part of the tRNA^Leu (UAA) gene containing a 240-nucleotidegroup I intron was amplified by PCR from cyanobacterium SynechococcusPCC 6301 genomic DNA. The pre-tRNA synthesized from the clonedPCR product was efficiently self-spliced in vitro under physiologicalconditions. The gene encoding the tRNA^Leu (UAA), trnL-UAA, wasisolated from a Synechococcus PCC 6301 genomic library and thenucleotide sequence of a 2,167-bp portion was determined. ThetrnL-UAA consists of a 34-bp 5' exon, a 240-bp group I intronand a 50-bp 3' exon. In addition, three open reading frames(ORF1, ORF2 and ORF3) were found in the 5' and 3' flanking regionsof trnL-UAA. The predicted protein sequence of ORF3, which islocated 74-bp upstream from trnL-UAA on the opposite strand,shows 66.2% amino acid identity to that of the SynechocystisPCC 6803 gene encoding subunit L of NADH dehydrogenase (ndhL).     

Plant peptide hormone phytosulfokine (PSK-alpha): synthesis of new analogues and their biological evaluation.

Phytosulfokine-alpha (PSK-alpha), a sulfated growth factor (H-Tyr(SO3H)-Ile-Tyr(SO3H)-Thr-Gln-OH) universally found in both monocotyledons and dicotyledons, strongly promotes proliferation of plant cells in culture. In our studies on structure/activity relationship in PSK-alpha the synthesis of a series of analogues was performed: [H-D-Tyr(SO3H)1]- (9), [H-Phe(4-SO3H)1]- (10), [H-D-Phe(4-SO3H)1]- (11), [H-Phg(4-SO3H)1]- (12), [H-D-Phg(4-SO3H)1]- (13), H-Phe(4-NHSO2CH3)1]- (14), [H-D-Phe(4-NHSO2CH3)1]- (15), [H-Phe(4-NO2)1]- (16), [H-D-Phe(4-NO2)1]- (17), [H-Phg(4-NO2)1]- (18), [H-D-Phg(4-NO2)1]- (19), [H-Hph(4-NO2)1]- (20), [H-Phg(4-OSO3H)1]- (21), [Phe(4-NO2)3]- (22), [Phg(4-NO2)3]- (23), [Hph(4-NO2)3]- (24), [H-Phe(4-SO3H)1, Phe(4-SO3H)3]- (25) [H-Phe(4-NO2)1, Phe(4-NO2)3]- (26), [H-Phg(4-NO2)1, Phg(4-NO2)3]- (27), [H-Hph(4-NO2)1, Hph(4-NO2)3]- (28) and [Val3]- PSK-alpha (29). For modification of the PSK-alpha peptide chain the novel amino acids and their derivatives were synthesized, such as: H-L-Phg(4-SO3H)-OH (1), H-D-Phg(4-SO3H)-OH (2), Fmoc-Phg(4-SO3H)-OH (3), Fmoc-D-Phg(4-SO3H)-OH (4), Boc-Phg(4-NHSO2CH3)-OH (5), Boc-D-Phg(4-NHSO2CH3)-OH (6) Boc-Phe(4-NHSO2CH3)-OH (7), and Boc-D-Phe(4-NHSO2CH3)-OH (8). Peptides were synthesized by a solid phase method according to the Fmoc procedure on a Wang-resin. Free peptides were released from the resin by 95% TFA in the presence of EDT. All peptides were tested by competitive binding assay to the carrot membrane using 3H-labelled PSK according to the Matsubayashi et al. test.     

Heterospecific sperm reduction in interspecific crosses between two closely related phytophagous ladybird beetles,Henosepilachna vigintioctomaculata and H. pustulosa (Coleoptera: Coccinellidae)

In interspecific crosses, a mismatch in internal physiological conditions between two species can reduce sperm viability in the interval from insemination to fertilization, leading to gametic isolation. Two closely related Japanese phytophagous ladybird beetles, Henosepilachna vigintioctomaculata and H. pustulosa, show several isolating barriers, including reduction in the number of heterospecific sperm in the female reproductive tract and low egg‐hatching rates in interspecific matings. However, the mechanisms of these two potential isolating barriers and the association between them are unknown. Here we investigated temporal changes in the number of sperm stored in the female reproductive tract and egg‐hatching rates in inter‐ and intraspecific crosses between these species. Although the number of sperm decreased after both inter‐ and intraspecific crosses, the reduction was more drastic in inter‐ than in intraspecific crosses for females of both species. Most of the sperm reduction occurred early on, during sperm transfer from the bursa copulatrix to the paired ampullae of the common oviduct (the sperm storage organs). These two species also demonstrated stably low egg‐hatching rates in interspecific crosses. Since the degree and timing of the sperm reduction did not correlate with egg‐hatching rates, the reduction in heterospecific sperm in interspecific crosses may not directly cause the low hatching rates. These two isolating barriers could be different expressions of the physiological mismatch and/or genetic incompatibility between gametes of these species.     

The enhancement of oxidative DNA damage by anti-diabetic metformin,buformin, and phenformin,via nitrogen-centered radicals

Metformin (N,N-dimethylbiguanide), buformin (1-butylbiguanide), and phenformin (1-phenethylbiguanide) are anti-diabetic biguanide drugs, expected to having anti-cancer effect. The mechanism of anti-cancer effect by these drugs is not completely understood. In this study, we demonstrated that these drugs dramatically enhanced oxidative DNA damage under oxidative condition. Metformin, buformin, and phenformin enhanced generation of 8-oxo-7,8-dihydro-2’-deoxyguanosine (8-oxodG) in isolated DNA reacted with hydrogen peroxide (H₂O₂) and Cu(II), although these drugs did not form 8-oxodG in the absence of H₂O₂ or Cu(II). An electron paramagnetic resonance (EPR) study, utilizing alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone and 3,3,5,5-tetramethyl-1-pyrroline-N-oxide as spin trapping agents, showed that nitrogen-centered radicals were generated from biguanides in the presence of Cu(II) and H₂O₂, and that these radicals were decreased by the addition of DNA. These results suggest that biguanides enhance Cu(II)/H₂O₂-mediated 8-oxodG generation via nitrogen-centered radical formation. The enhancing effect on oxidative DNA damage may play a role on anti-cancer activity.     

Brain-derived neurotrophic factor (BDNF) induces antagonistic action to Nogo signaling by the upregulation of lateral olfactory tract usher substance (LOTUS) expression

Neurons in the central nervous system (CNS) have limited capacity for axonal regeneration after trauma and neurological disorders due to an endogenous nonpermissive environment for axon regrowth in the CNS. Lateral olfactory tract usher substance (LOTUS) contributes to axonal tract formation in the developing brain and axonal regeneration in the adult brain as an endogenous Nogo receptor-1 (NgR1) antagonist. However, how LOTUS expression is regulated remains unclarified. This study examined molecular mechanism of regulation in LOTUS expression and found that brain-derived neurotrophic factor (BDNF) increased LOTUS expression in cultured hippocampal neurons. Exogenous application of BDNF increased LOTUS expression at both mRNA and protein levels in a dose-dependent manner. We also found that pharmacological inhibition with K252a and gene knockdown by siRNA of tropomyosin-related kinase B (TrkB), BDNF receptor suppressed BDNF-induced increase in LOTUS expression. Further pharmacological analysis of the TrkB signaling pathway revealed that BDNF increased LOTUS expression through mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K) cascades, but not phospholipase C-γ (PLCγ) cascade. Additionally, treatment with c-AMP response element binding protein (CREB) inhibitor partially suppressed BDNF-induced LOTUS expression. Finally, neurite outgrowth assay in cultured hippocampal neurons revealed that BDNF treatment-induced antagonism for NgR1 by up-regulating LOTUS expression. These findings suggest that BDNF may acts as a positive regulator of LOTUS expression through the TrkB signaling, thereby inducing an antagonistic action for NgR1 function by up-regulating LOTUS expression. Also, BDNF may synergistically affect axon regrowth through the upregulation of LOTUS expression.