Differential metabolisms of green leaf volatiles in injured and intact parts of a wounded leaf meet distinct ecophysiological requirements

Almost all terrestrial plants produce green leaf volatiles (GLVs), consisting of six-carbon (C6) aldehydes, alcohols and their esters, after mechanical wounding. C6 aldehydes deter enemies, but C6 alcohols and esters are rather inert. In this study, we address why the ability to produce various GLVs in wounded plant tissues has been conserved in the plant kingdom. The major product in completely disrupted Arabidopsis leaf tissues was (Z)-3-hexenal, while (Z)-3-hexenol and (Z)-3-hexenyl acetate were the main products formed in the intact parts of partially wounded leaves. (13)C-labeled C6 aldehydes placed on the disrupted part of a wounded leaf diffused into neighboring intact tissues and were reduced to C6 alcohols. The reduction of the aldehydes to alcohols was catalyzed by an NADPH-dependent reductase. When NADPH was supplemented to disrupted tissues, C6 aldehydes were reduced to C6 alcohols, indicating that C6 aldehydes accumulated because of insufficient NADPH. When the leaves were exposed to higher doses of C6 aldehydes, however, a substantial fraction of C6 aldehydes persisted in the leaves and damaged them, indicating potential toxicity of C6 aldehydes to the leaf cells. Thus, the production of C6 aldehydes and their differential metabolisms in wounded leaves has dual benefits. In disrupted tissues, C6 aldehydes and their α,β-unsaturated aldehyde derivatives accumulate to deter invaders. In intact cells, the aldehydes are reduced to minimize self-toxicity and allow healthy cells to survive. The metabolism of GLVs is thus efficiently designed to meet ecophysiological requirements of the microenvironments within a wounded leaf.     

Lack of Significant Elevation of Myeloid-Derived Suppressor Cells in Peripheral Blood of Chronically Hepatitis C Virus-Infected Individuals

Myeloid-derived suppressor cells (MDSC) are immature myeloid cells with immunosuppressive function. Compared to the level in healthy controls (HC), no elevation of MDSC in chronic hepatitis C (cHEP-C) patients was found, and there was no difference in MDSC based on genotype or viral load (P > 0.25). Moreover, MDSC of cHEP-C patients inhibited CD8 T cell function as efficiently as MDSC of HC did. Since we detected neither quantitative nor qualitative differences in MDSC of cHEP-C patients relative to those of HC, we postulate that MDSC in peripheral blood are most likely not significant regarding immune dysfunction in cHEP-C.     

Enantioselectivity of bunitrolol 4‐hydroxylation is reversed by the change of an amino acid residue from valine to methionine at position 374 of cytochrome P450‐2D6

The enantioselectivity of 4‐hydroxylation of bunitrolol (BTL), a β‐adrenoceptor blocking drug, was studied in microsomes from human liver, human hepatoma (Hep G2) cells expressing CYP2D6, and lymphoblastoid cells expressing CYP2D6. Kinetics in human liver microsomes showed that the Vmax value for (+)‐BTL was 2.1‐fold that of (−)‐BTL, and that the Km value for (+)‐BTL was lower than that for the (−)‐antipode, resulting in the intrinsic clearance (Vmax/Km) of (+)‐BTL being 2.1‐fold over its (−)‐antipode. CYP2D6 (CYP2D6‐met) expressed in Hep G2 cells had a methionine residue at position 373 of the amino acid sequence and a rat‐type N‐terminal peptide (MELLNGTGLWSM) instead of the human‐type (MGLEALVPLAVIV), and showed enantioselectivity of [(+)‐BTL < (−)‐BTL] for the rate of BTL 4‐hydroxylation. In contrast, enantioselectivity [(+)‐BTL > (−)‐BTL] for Hep G2‐CYP2D6 (CYP2D6‐val) with a human‐type N‐terminal peptide that had a valine residue at 374, which corresponds to the methionine of the CYP2D6‐met variant, was the same as that for human liver microsomes. We further confirmed that CYP2D6‐met and CYP2D6‐val expressed in human lymphoblastoid cells, both of which have methionine and valine, respectively, at position 374 and a human‐type N‐terminal peptide, exhibited the same enantioselectivities as those obtained from CYP2D6‐met and CYP2D6‐val expressed in the Hep G2 cell system. These results indicate that the amino acid at 374 of CYP2D6 is one of the key factors influencing the enantioselectivity of BTL 4‐hydroxylation. Chirality 11:1–9, 1999. © 1999 Wiley‐Liss, Inc.     

Functional analysis of protein disulfide isomerases in blood feeding, viability and oocyte development in Haemaphysalis longicornis ticks

Three protein disulfide isomerases from Haemaphysalis longicornis ticks (designated as HlPDI-1, HlPDI-2, and HlPDI-3) were previously identified. In order to further analyze their biological functions, the dsRNA of each HlPDI gene and one dsRNA combination of HlPDI-1/HlPDI-3 were separately injected into female ticks. Reduction of gene and protein expression of HlPDIs by RNA interference (RNAi) was demonstrated by real-time PCR, RT-PCR and Western blot analysis. In single dsRNA-injected groups, HlPDI-1 RNAi impacted tick blood feeding and oviposition, HlPDI-2 RNAi impacted tick viability and HlPDI-3 RNAi had no significant impact by itself. However, the injection of a combination of HlPDI-1/HlPDI-3 dsRNA had synergistic effects on tick viability. Furthermore, the midgut and cuticle were severely damaged in HlPDI-2 dsRNA-injected ticks and HlPDI-1/HlPDI-3 dsRNA-injected ticks, respectively, and disruption of HlPDI genes led to a significant reduction of disulfide bond-containing vitellogenin (Vg) expression in ticks. These results indicate that PDIs from H. longicornis are involved in blood feeding, viability and oocyte development, probably by mediating the formation of disulfide bond-containing proteins of the ticks and the formation of basement membrane and cuticle components such as extracellular matrix (ECM). This is the first report on the functional analysis of PDI family molecules as well as the interactions of PDI and other molecules in blood-feeding arthropods.     

Sept8 controls the binding of vesicle-associated membrane protein 2 to synaptophysin

Septins, a conserved family of GTP/GDP-binding proteins, are present in organisms as diverse as yeast and mammals. We analyzed the distribution of five septins, Sept6, Sept7, Sept8, Sept9 and Sept11, in various rat tissues by western blot analyses and found all septins to be expressed in brain. We also examined the developmental changes of expression of these septins in the rat brain and found that the level of Sept8 increased during post-natal development. Morphological analyses revealed that Sept8 is enriched at pre-synapses. Using yeast two-hybrid screening, we identified vesicle-associated membrane protein 2 (VAMP2), a soluble N -ethylmaleimide-sensitive factor attachment protein receptor (SNARE), as an interacting protein for Sept8. Synaptophysin is reported to associate with and recruit VAMP2 to synaptic vesicles and dissociate prior to forming the SNARE complex consisting of VAMP2, syntaxin and synaptosome-associated protein of 25 kDa. We showed that Sept8 suppresses the interaction between VAMP2 and synaptophysin through binding to VAMP2. In addition, we found that Sept8 forms a complex with syntaxin1A, and the Sept8-VAMP2 interaction is disrupted by synaptosome-associated protein of 25 kDa. These results suggest that Sept8 may participate in the process of the SNARE complex formation and subsequent neurotransmitter release.     

Glycosaminoglycan affinity of the complete fibroblast growth factor family

BACKGROUND: Many fibroblast growth factor family proteins (FGFs) bind to the heparan sulfate/heparin (HP) subtypes of sulfated glycosaminoglycans (GAGs), and a few have recently been reported to also interact with chondroitin sulfate (CS), another sulfated GAG subtype. METHODS: To gain additional insight into this interaction, we prepared all currently known FGFs (i.e., FGF1-FGF23) and assessed their affinity for HP, CS-B, CS-D and CS-E. In addition, midkine, hepatocyte growth factor and pleiotrophin were studied as other known HP-binding proteins. RESULTS: We found that members of the FGF19 subfamily (i.e., FGF15, 19, 21 and 23) had little or no affinity for HP; all of the other secretable growth factors tested had strong affinities for HP, as was indicated by the finding that their elution from HP-Sepharose columns required 1.0-1.5 M NaCl. We also found that FGF3, 6, 8 and 22 had strong affinities for CS-E, while FGF5 had a moderate affinity for CS-D. The interactions between FGFs and GAGs thus appear to be more diverse than previously understood. GENERAL SIGNIFICANCE: This is noteworthy, as the differential interactions of these growth factors with GAGs may be key determinants of their specific biological activities.     

Experience of plant infestation by the omnivorous arthropod <Emphasis Type="Italic">Nesidiocoris tenuis</Emphasis> affects its subsequent responses to prey-infested plant volatiles

Nesidiocoris tenuis, an omnivorous arthropod, infests plants in either the absence or presence of prey arthropods. We studied whether plant-infestation experience of N. tenuis affected its subsequent prey-finding behavior. We used sesame plants and eggplants as food plants for N. tenuis, and common cutworm (CCW) (Spodoptera litura larvae) as prey. We focused on their olfactory response to CCW-infested sesame plants versus CCW-infested eggplants in a Y-tube olfactometer. When N. tenuis adults experienced the infestation of sesame plants for one day, they preferred volatiles from CCW-infested sesame plants to those from CCW-infested eggplants. By contrast, when N. tenuis experienced the infestation of eggplants for one day, they showed no difference in their preference between the two odor sources. When the duration of the infestation of plants was increased to four days, N. tenuis that had experienced sesame plants showed a reversed response: they preferred CCW-infested eggplant volatiles, while those that had infested eggplants again showed no difference in their preference. Next, we studied the olfactory preference of N. tenuis that had previously infested plants with moth (Ephestia kuehniella) eggs. We found that irrespective of plant species and of duration of experience (either one or four days), N. tenuis adults that had previously experienced one plant species showed a significant preference for volatiles from CCW-infested plants of the same species. The blends of the volatiles emitted from CCW-infested sesame plants and those from CCW-infested eggplants were qualitatively different. Possibility to control the olfactory response of N. tenuis to certain prey-infested plant volatiles by adjusting their feeding history is discussed.     

Using CRISPRs as a metagenomic tool to identify microbial hosts of a diffuse flow hydrothermal vent viral assemblage

Metagenomic analyses of viruses have revealed widespread diversity in the viriosphere, but it remains a challenge to identify specific hosts for a viral assemblage. To address this problem, we analyze the viral metagenome of a northeast Pacific hydrothermal vent with a comprehensive database of spacers derived from the clustered regularly interspaced short palindromic repeat (CRISPR) putative immune system. CRISPR spacer matches to the marine vent virome suggest that viruses infecting hosts from diverse taxonomic groups are present in this vent environment. Comparative virome analyses show that CRISPR spacers from vent isolates and from thermophiles in general have a higher percentage of matches to the vent virome than to other marine or terrestrial hot spring viromes. However, a high percentage of hits to spacers from mesophilic hosts, combined with a moderately high modeled alpha diversity, suggest that the marine vent virome is comprised of viruses that have the potential to infect diverse taxonomic groups of multiple thermal regimes in both the bacterial and the archaeal domains.