P450s in plant-insect interactions

Cytochrome P450 monooxygenases (P450s) are integral in defining the relationships between plants and insects. Secondary metabolites produced in plants for protection against insects and other organisms are synthesized via pathways that include P450s in many different families and subfamilies. Survival of insects in the presence of toxic secondary metabolites depends on their metabolism by more limited groups of P450s. Examples of functionally characterized plant and insect P450s known to be involved in these interactions are discussed in terms of their diversities, reactivities and regulators. These and future examples, which will be uncovered as the fields of plant biology and entomology converge on this interesting area, provide much insight into the array of plant metabolites that are mainline defenses against insects, the range of insect monooxygenases that inactivate these compounds and the evolutionary processes occurring as these organisms wage daily battles with one another. Molecular perspectives on these interactions will provide the scientific community with information critical for genetic manipulation of these organisms aimed at enhancing plant resistance to insects and eliminating insect resistance to natural plant toxins and synthetic insecticides.     

Comparison of male and female emerald ash borer (Coleoptera: Buprestidae) responses to phoebe oil and (Z)-3-hexenol lures in light green prism traps

We conducted trapping experiments for the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) in Michigan, U.S.A., and Ontario, Canada, to compare unbaited light green sticky prism traps with traps baited with phoebe oil, (Z)-3-hexenol (Z3-6:OH), or blends of other green leaf volatiles (GLVs) with Z3-6:OH. Traps were placed in the lower canopy of ash trees (Fraxinus spp.). Catches with Z3-6:OH-baited traps showed a significant male bias and these traps caught significantly more males than the unbaited controls at both sites. They were also superior to phoebe oil-baited traps and those baited with GLV blends. Catches with phoebe oil showed a significant female bias but there was no difference in the number of females captured between traps baited with phoebe oil or Z3-6:OH lures. Catches were analyzed at regular time intervals to examine the response of A. planipennis to the lures over the course of the flight season. Z3-6:OH-baited traps consistently caught more males than the controls at each interval throughout the flight season. Catches of females with Z3-6:OH and phoebe oil were significantly better than the controls early in the flight season but declined to control levels by midseason. Our results suggest that Z3-6:OH-baited green traps placed in the ash canopy would be a superior lure for detecting and monitoring A. planipennis throughout the flight season.     

Novel substituted (Z)-2-(N-benzylindol-3-ylmethylene)quinuclidin-3-one and (Z)-(+/-)-2-(N-benzylindol-3-ylmethylene)quinuclidin-3-ol derivatives as potent thermal sensitizing agents

Use of ionizing radiation is essential for the management of many human cancers, and therapeutic hyperthermia has been identified as a potent radiosensitizer. Radiation therapy combined with adjuvant hyperthermia represents a potential tool to provide outstanding local-regional control for refractory disease. (Z)-(±)-2-(N-Benzylindol-3-ylmethylene)quinuclidin-3-ol (2) and (Z)-(±)-2-(N-benzenesulfonylindol-3-ylmethylene)quinuclidin-3-ol (4) were initially identified as potent thermal sensitizers that could lower the threshold needed for thermal sensitivity to radiation treatment. To define the structural requirements of the molecule that are essential for thermal sensitization, we have synthesized and evaluated a series of (Z)-2-(N-benzylindol-3-ylmethylene)quinuclidin-3-one (9), and (Z)-(±)-2-(N-benzylindol-3-ylmethylene)quinuclidin-3-ol (10) analogs that incorporate a variety of substituents in both the indole and N-benzyl moieties. These systematic structure–activity relationship (SAR) studies were designed to further the development and optimization of potential clinically useful thermal sensitizing agents. The most potent analog was compound 10 (R¹ = H, R² = 4-Cl), which potently inhibited (93% inhibition at 50 μM) the growth of HT-29 cells after a 41 °C/2 h exposure.     

Population dynamics models in plant-insect herbivore-pesticide interactions

We consider several population dynamics models in investigating data from controlled experiments with aphids in broccoli patches surrounded by different margin types (bare or weedy ground) and three levels of insecticide spray (no, light, or heavy spray). We carry out parameter estimation computations along with statistical analysis to compare autonomous versus non-autonomous model dynamics. We conclude with a brief discussion of some not-so-subtle pitfalls that can arise when using quantitative measures of model fit-to-data to make biological inferences as well as offer a positive example of how one might combine a priori biological hypothesis and intuition with rather sophisticated (from a field biology viewpoint) mathematical methodologies to suggest synergisms.     

Solar ultraviolet-B radiation affects plant-insect interactions in a natural ecosystem of Tierra del Fuego (southern Argentina)

We examined the effects of solar ultraviolet-B radiation (UVB) on plant-herbivore interactions in native ecosystems of the Tierra del Fuego National Park (southern Argentina), an area of the globe that is frequently under the Antarctic “ozone hole” in early spring. We found that filtering out solar UVB from the sunlight received by naturally-occurring plants of Gunnera magellanica, a creeping perennial herb, significantly increased the number of leaf lesions caused by chewing insects. Field surveys suggested that early-season herbivory was principally due to the activity of moth larvae (Lepidoptera: Noctuidae). Manipulative field experiments showed that exposure to solar UVB changes the attractiveness of G. magellanica leaf tissue to natural grazers. In a laboratory experiment, locally caught moth caterpillars tended to eat more tissue from leaves grown without UVB than from leaves exposed to natural UVB during development; however, the difference between treatments was not significant. Leaves grown under solar UVB had slightly higher N levels than leaves not exposed to UVB; no differences between UVB treatments in specific leaf mass, relative water content, and total methanol-soluble phenolics were detected. Our results show that insect herbivory in a natural ecosystem is influenced by solar UVB, and that this influence could not be predicted from crude measurements of leaf physical and chemical characteristics and a common laboratory bioassay. Received: 4 December 1997 / Accepted: 12 May 1998     

1-N-methyl-(6E)-(2-methylpropylidene)-(3Z)-3-(phenylmethylene)-2,5-piperazinedione,a metabolite from Streptomyces albus

The structure and stereochemistry of a new piperazinedione, isolated from the cells of Streptomyces albus, are assigned on the basis of spectroscopic data, including comparison with related 2,5-piperazinediones.     

Hydroperoxy-arachidonic acid mediated n-hexanal and (Z)-3- and (E)-2-nonenal formation in Laminaria angustata

In higher plants, C6 and C9 aldehydes are formed from C18 fatty acids, such as linoleic or linolenic acid, through formation of 13- and 9-hydroperoxides, followed by their stereospecific cleavage by fatty acid hydroperoxide lyases (HPL). Some marine algae can also form C6 and C9 aldehydes, but their precise biosynthetic pathway has not been elucidated fully. In this study, we show that Laminaria angustata, a brown alga, formed C6 and C9 aldehydes enzymatically. The alga forms C9 aldehydes exclusively from the C20 fatty acid, arachidonic acid, while C6 aldehydes are derived either from C18 or from C20 fatty acid. The intermediates in the biosynthetic pathway were trapped by using a glutathione/glutathione peroxidase system, and subjected to structural analyses. Formation of (S)-12-, and (S)-15-hydroperoxy arachidonic acids [12(S)HPETE and 15(S)HPETE] from arachidonic acid was confirmed by chiral HPLC analyses. These account respectively for C9 aldehyde and C6 aldehyde formation, respectively. The HPL that catalyzes formation of C9 aldehydes from 12(S)HPETE seems highly specific for hydroperoxides of C20 fatty acids.     

Novel Synthesis of (Z)-3-Hexen-1-ol and cis-Jasmone

Both (Z)-3-hexen-1-ol and cis-jasmone were synthesised via 1,4-selective hydrogenation of conjugated dienes in the presence of arene Cr(CO)₃ or Cr(CO)₆ catalysts as the key step.     

Intermittent exposure to traces of green leaf volatiles triggers the production of (Z)-3-hexen-1-yl acetate and (Z)-3-hexen-1-ol in exposed plants

Intermittent exposure during a period of 3 weeks of undamaged Arabidopsis plants to trace amounts of volatiles emitted by freshly damaged Arabidopsis plants resulted in an increase of subsequent artificial-damage-induced production of (Z)-3-hexen-1-yl acetate and (Z)-3-hexen-1-ol in the exposed Arabidopsis plants when compared with Arabidopsis plants exposed to undamaged Arabidopsis plant volatiles (control plants). We previously showed that (Z)-3-hexen-1-yl acetate attracts a parasitic wasp, Cotesia glomerata. Thus, the induced production of this volatile explained our previously reported finding that, when artificially damaged, the exposed plants were more attractive to C. glomerata than control plants.     

Synthesis and antitumor activity of 5-[1-(3-(dimethylamino)propyl)-5-halogenated-2-oxoindolin-(3Z)-ylidenemethyl]-2,4-dimethyl-1H-pyrrole-3-carboxamides

We report herein the design and synthesis of novel 1-[3-(dimethylamino)propyl]indolin-2-one derivatives based on the structural features of Sunitinib, a known multitargeted receptor tyrosine kinase inhibitor, and TMP-20, a previously discovered compound with good antitumor activity in our lab. These newly synthesized derivatives were evaluated for in vitro activity against five human cancer cell lines and VEGF/bFGF-stimulated HUVECs. Results revealed that all of the target compounds 1a-p show potent antitumor activity, compounds 1e-h (IC₅₀’s: 0.45-5.08 μM) are more active than Sunitinib (IC₅₀’s: 1.35-6.61 μM), and the most active compound 1h (IC₅₀: 0.47-3.11 μM) is 2.1-4.6-fold more potent than Sunitinib against all five cancer cell lines. In addition, like Sunitinib, 1a-p have higher selectivity on VEGF-stimulated HUVEC other than bFGF-stimulated HUVEC.     

Sequential substitution of 1,2-dichloro-ethene: a convenient stereoselective route to (9Z,11E)-, (10E,12Z)- and (10Z,12Z)-

Conjugated linoleic acid (CLA) isomers are present in human foods derived from milk or ruminant meat. To study their metabolism, (9Z,11E)-, (10E,12Z)- and (10Z,12Z)-[1-(14)C]-octadecadienoic acids with high radiochemical and isomeric purities (>98%) were prepared by stereoselective multi-step syntheses involving sequential substitution of 1,2-dichloro-ethene. In the case of the (9Z,11E) isomer, a first metal-catalyzed cross-coupling reaction between (E)-1,2-dichloro-ethene and 2-non-8-ynyloxy-tetrahydro-pyran, obtained from 7-bromo-heptan-1-ol, gave a conjugated chloroenyne. A second coupling reaction with hexylmagnesium bromide provided a heptadecenynyl derivative. Stereoselective reduction of the triple bond and bromination afforded (7E,9Z)-17-bromo-heptadeca-7,9-diene. Formation of the Grignard reagent and carbonation with 14CO(2) gave (9Z,11E)-[1-(14)C]-octadeca-9,11-dienoic acid (overall yield from 7-bromo-heptan-1-ol, 14.4%). (10E,12Z)- and (10Z,12Z)-[1-(14)C]-octadeca-10,12-dienoic acids were synthesized by the same methodology using 1-heptyne, 8-bromo-octan-1-ol and, respectively, (E)-1,2-dichloro-ethene and its (Z) isomer (overall yield from 8-bromo-octan-1-ol, 13.1% (10E,12Z); 17.2% (10Z,12Z)). Impurities (<2% if present) were identified as being (E,E) CLA isomers and were removed by RP-HPLC. Metabolism studies in animal are in progress.     

Synthesis and antiherpetic activity of (Z)- and (E)-isomers of 9-(3-phosphonomethoxyprop-1-en-yl)adenine

9-(3-Phosphonomethoxyprop-1-en-yl)adenine (Z)- and (E)-isomers were synthesized. The stereoselectivity of double bond formation was studied by variation of sulfonyl groups. The resulting phosphonates exhibited a moderate antiherpetic activity in a culture of Vero cells infected with herpes simplex type 1 virus. The Z-isomer was shown to be more effective inhibitor of virus reproduction in the case of both wild and acyclovir-resistant strain.     

Facile syntheses for (5Z,9Z)-5,9-hexadecadienoic acid, (5Z,9Z)-5,9-nonadecadienoic acid, and (5Z,9Z)-5,9-eicosadienoic acid through a common synthetic route

The delta 5,9 fatty acids (5Z,9Z)-5,9-hexadecadienoic acid, (5Z,9Z)-5,9-nonadecadienoic acid, and (5Z,9Z)-5,9-eicosadienoic acid were synthesized for the first time in four steps (9-12% overall yield) starting from commercially available 2-(2-bromoethyl)-1,3-dioxolane. The synthetic approach provided enough material to corroborate the structure and stereochemistry of (5Z,9Z)-5,9-nonadecadienoic acid which was recently identified in the flowers of Malvaviscus arboreus (Malvaceae). The novel phospholipids 1-hexadecanoyl-2-[(5Z,9Z)-5,9-eicosadienoyl]-sn-glycer o-3-phosphocholine and 1-octadecanoyl-2-[(5Z,9Z)-5,9-eicosadienoyl]-sn- glycero-3-phosphocholine were also synthesized from commercially available L-alpha-phosphatidylcholine (egg yolk) and characterized by positive ion electrospray mass spectrometry. These are the first examples of unsymmetrical phospholipids with saturated fatty acids at the sn-1 position and delta 5,9 fatty acids at the sn-2 position.     

(Z)-3-Hexenol Induces Tea Defense against Ectropis grisescens in the Field

Russian Journal of Plant Physiology - The tea geometrid Ectropis grisescens is an important pest of tea plant (Camellia sinensis (L.) O.&nbsp;Kuntze). It feeds on the new leaves and tender...