Accumulation of HDMBOA-Glc is induced by biotic stresses prior to the release of MBOA in maize leaves

The effects of biotic stresses on the contents of benzoxazinones (Bxs) were investigated in maize leaves. When the causal agent of southern corn leaf blight, Bipolaris maydis, was inoculated on the third leaf, the amount of 2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one glucoside (HDMBOA-Glc) increased, reaching a maximum level 48 h after inoculation. The inoculation of weakly pathogenic Curvularia lunata and non-pathogenic Alternaria alternata also resulted in accumulation of HDMBOA-Glc, and filtrates of the cultures of B. maydis, C. lunata and A. alternata also showed the accumulation of elicitor-active compounds by the fungi. Furthermore the infection of B. maydis induced formation of dark brown lesions, where most abundant Bx-related compound was 6-methoxy-2-benzoxazolinone (MBOA). The later is formed by degradation of DIMBOA and HDMBOA, whereas HDMBOA-Glc was most abundant in the surrounding green tissues. Among the Bx-related compounds, MBOA exhibited the strongest inhibition of the germination of the conidia and of the growth of germ tubes of B. maydis, C. lunata and A. alternata. In addition to fungal infection, the feeding by rice armyworm larvae resulted in HDMBOA-Glc accumulation. These findings are discussed in relation to the possible ecological relevance of the conversion of DIMBOA-Glc into HDMBOA-Glc.     

Formation of unidentified nitrogen in plants: an implication for a novel nitrogen metabolism

Plants take up inorganic nitrogen and store it unchanged or convert it to organic forms. The nitrogen in such organic compounds is stoichiometrically recoverable by the Kjeldahl method. The sum of inorganic nitrogen and Kjeldahl nitrogen has long been known to equal the total nitrogen in plants. However, in our attempt to study the mechanism of nitrogen dioxide (NO₂) metabolism, we unexpectedly discovered that about one-third of the total nitrogen derived from ¹⁵N-labeled NO₂ taken up by Arabidopsis thaliana (L.) Heynh. plants was converted to neither inorganic nor Kjeldahl nitrogen, but instead to an as yet unknown nitrogen compound(s). We here refer to this nitrogen as unidentified nitrogen (UN). The generality of the formation of UN across species, nitrogen sources and cultivation environments for plants has been shown as follows. Firstly, all of the other 11 plant species studied were found to form the UN in response to fumigation with ¹⁵NO₂. Secondly, tobacco (Nicotiana tabacum L.) plants fed with ¹⁵N-nitrate appeared to form the UN. And lastly, the leaves of naturally fed vegetables, grass and roadside trees were found to possess the UN. In addition, the UN appeared to comprise a substantial proportion of total nitrogen in these plant species. Collectively, all of our present findings imply that there is a novel nitrogen mechanism for the formation of UN in plants. Based on the analyses of the exhaust gas and residue fractions of the Kjeldahl digestion of a plant sample containing the UN, probable candidates for compounds that bear the UN were deduced to be those containing the heat-labile nitrogen–oxygen functions and those recalcitrant to Kjeldahl digestion, including organic nitro and nitroso compounds. We propose UN-bearing compounds may provide a chemical basis for the mechanism of the reactive nitrogen species (RNS), and thus that cross-talk may occur between UN and RNS metabolisms in plants. A mechanism for the formation of UN-bearing compounds, in which RNS are involved as intermediates, is proposed. The important broad impact of this novel nitrogen metabolism, not only on the general physiology of plants, but also on plant substances as human and animal food, and on plants as an integral part of the global environment, is discussed.Abbreviations NO Nitric oxide - NO₂ Nitrogen dioxide - RNS Reactive nitrogen species - UN Unidentified nitrogen - TNNAT, RNNAT, INNAT and UNNAT Total, Kjeldahl, inorganic and unidentified nitrogen in naturally fed plants, respectively - TNNIT, RNNIT, INNIT and UNNIT Total, Kjeldahl, inorganic and unidentified nitrogen derived from nitrate, respectively - TNNO2, RNNO2, INNO2 and UNNO2 Total, Kjeldahl, inorganic and unidentified nitrogen derived from NO₂, respectively     

Tie2/angiopoietin-1 signaling regulates hematopoietic stem cell quiescence in the bone marrow niche

The quiescent state is thought to be an indispensable property for the maintenance of hematopoietic stem cells (HSCs). Interaction of HSCs with their particular microenvironments, known as the stem cell niches, is critical for adult hematopoiesis in the bone marrow (BM). Here, we demonstrate that HSCs expressing the receptor tyrosine kinase Tie2 are quiescent and antiapoptotic, and comprise a side-population (SP) of HSCs, which adhere to osteoblasts (OBs) in the BM niche. The interaction of Tie2 with its ligand Angiopoietin-1 (Ang-1) induced cobblestone formation of HSCs in vitro and maintained in vivo long-term repopulating activity of HSCs. Furthermore, Ang-1 enhanced the ability of HSCs to become quiescent and induced adhesion to bone, resulting in protection of the HSC compartment from myelosuppressive stress. These data suggest that the Tie2/Ang-1 signaling pathway plays a critical role in the maintenance of HSCs in a quiescent state in the BM niche.     

Significance of low-frequency local fluctuation motions in the transmembrane B and C α-helices of bacteriorhodopsin,to facilitate efficient proton uptake from the cytoplasmic surface,as revealed by site-directed solid-state <Superscript>13</Superscript>C NMR

¹³C NMR spectra of [1-¹³C]Val- or -Pro-labeled bacteriorhodopsin (bR) and its single or double mutants, including D85N, were recorded at various pH values to reveal conformation and dynamics changes in the transmembrane -helices, in relation to proton release and uptake between bR and the M-like state caused by modified charged states at Asp85 and the Schiff base (SB). It was found that the D85N mutant acquired local fluctuation motion with a frequency of 10⁴ Hz in the transmembrane B -helix, concomitant with deprotonation of SB in the M-like state at pH 10, as manifested from a suppressed ¹³C NMR signal of the [1-¹³C]-labeled Val49 residue. Nevertheless, local dynamics at Pro50 neighboring with Val49 turned out to be unchanged, irrespective of the charged state of SB as viewed from the ¹³C NMR of [1-¹³C]-labeled Pro50. This means that the transmembrane B -helix is able to acquire the fluctuation motion with a frequency of 10⁴ Hz beyond the kink at Pro50 in the cytoplasmic side. Concomitantly, fluctuation motion at the C helix with frequency in the order of 10⁴ Hz was found to be prominent, due to deprotonation of SB at pH 10, as viewed from the ¹³C NMR signal of Pro91. Accordingly, we have proposed here a novel mechanism as to proton uptake and transport based on a dynamic aspect that a transient environmental change from a hydrophobic to hydrophilic nature at Asp96 and SB is responsible for the reduced pK_a value which makes proton uptake efficient, as a result of acquisition of the fluctuation motion at the cytoplasmic side of the transmembrane B and C -helices in the M-like state. Further, it is demonstrated that the presence of a van der Waals contact of Val49 with Lys216 at the SB is essential to trigger this sort of dynamic change, as revealed from the ¹³C NMR data of the D85N/V49A mutant.     

Essential structural features of acetogenins: role of hydroxy groups adjacent to the bis-THF rings

The presence of two hydroxy groups adjacent to the THF ring(s) is a common structural feature of natural acetogenins. To elucidate the role of each hydroxy group in the inhibitory action of acetogenins, we synthesized three acetogenin analogues which lack either or both of the hydroxy groups, and investigated their inhibitory activities with bovine heart mitochondrial complex I. Our results indicate that the presence of either of the two hydroxy groups sufficiently sustains a potent inhibitory effect.     

Orally active anti-proliferation agents: novel diphenylamine derivatives as FGF-R2 autophosphorylation inhibitors

(6,7-Disubstituted-quinolin-4-yloxy-phenyl)(4-substituted-phenyl)amine derivatives were synthesized and evaluated by a cellular autophosphorylation assay for FGF-R2 in the human scirrhous gastric carcinoma cell line, OCUM-2MD3. We also performed metabolic stability studies showing that substitutions at the 7-position of quinoline affect its biological stability. In this study, we achieved a remarkable improvement in the solubility and metabolic stability of the diphenylamine derivative. The most promising compound 15e showed a significant decrease in tumor volume when orally administered.     

Essential role for the p40 subunit of interleukin-12 in neutrophil-mediated early host defense against pulmonary infection with Streptococcus pneumoniae: involvement of interferon-gamma

Interleukin (IL)-12 is a critical cytokine in the T helper (Th)1 response and host defense against intracellular microorganisms, while its role in host resistance to extracellular bacteria remains elusive. In the present study, we elucidated the role of IL-12 in the early-phase host defense against acute pulmonary infection with Streptococcus pneumoniae, a typical extracellular bacterium, using IL-12p40 gene-disrupted (IL-12p40KO) mice. IL-12p40KO mice were highly susceptible to S. pneumoniae infection, as indicated by the shortened survival time, which was completely restored by the replacement therapy with recombinant (r) IL-12, and increased bacterial counts in the lung. In these mice, recruitment of neutrophils in the lung was significantly attenuated when compared to that in wild-type (WT) mice, which correlated well with the reduced production of macrophage inflammatory protein (MIP-2) and tumor necrosis factor (TNF)-alpha in the infected tissues at the early phase of infection. In vitro synthesis of both cytokines by S. pneumoniae-stimulated lung leukocytes was significantly lower in IL-12p40KO mice than in WT mice, and addition of rIL-12 or interferon (IFN)-gamma restored the reduced production of MIP-2 and TNF-alpha in IL-12p40KO mice. Neutralizing anti-IFN-gamma monoclonal antibody (mAb) significantly decreased the effect of rIL-12. Anti-IFN-gamma mAb shortened the survival time of infected mice and reduced the recruitment of neutrophils and production of MIP-2 and TNF-alpha in the lungs. Our results indicated that IL-12p40 plays a critical role in the early-phase host defense against S. pneumoniae infection by promoting the recruitment of neutrophils to the infected tissues.     

Complete nucleotide sequence and gene rearrangement of the mitochondrial genome of the bell-ring frog, Buergeria buergeri (family Rhacophoridae)

In this study we determined the complete nucleotide sequence (19,959 bp) of the mitochondrial DNA of the rhacophorid frog Buergeria buergeri. The gene content, nucleotide composition, and codon usage of B. buergeri conformed to those of typical vertebrate patterns. However, due to an accumulation of lengthy repetitive sequences in the D-loop region, this species possesses the largest mitochondrial genome among all the vertebrates examined so far. Comparison of the gene organizations among amphibian species (Rana, Xenopus, salamanders and caecilians) revealed that the positioning of four tRNA genes and the ND5 gene in the mtDNA of B. buergeri diverged from the common vertebrate gene arrangement shared by Xenopus, salamanders and caecilians. The unique positions of the tRNA genes in B. buergeri are shared by ranid frogs, indicating that the rearrangements of the tRNA genes occurred in a common ancestral lineage of ranids and rhacophorids. On the other hand, the novel position of the ND5 gene seems to have arisen in a lineage leading to rhacophorids (and other closely related taxa) after ranid divergence. Phylogenetic analysis based on nucleotide sequence data of all mitochondrial genes also supported the gene rearrangement pathway.