Effect of host diet on acceptance of eastern spruce budworm eggs byTrichogramma minutum

The acceptance behaviour of the parasitic wasp, Trichogramma minutum Riley (Hymenoptera: Trichogrammatidae), was studied on two types of egg masses of eastern spruce budworm (SBW), Choristoneura fumiferana Clemens. Host eggs were obtained from moths that had been fed balsam fir or artificial diet during their larval stages. Parasitoids were reared from both types of hosts. Host acceptance assays were conducted where females were provided with a single egg mass and with a choice between egg masses. Regardless of the parasitoid's rearing host, females parasitised hosts reared from artificial diet more often than those from balsam fir. Response was consistent in both no-choice and choice assays. Rejection of hosts tended to occur during the examining stage of behaviour, suggesting that acceptability is judged externally. If a host was accepted, the same number of eggs were laid per egg mass regardless of treatment.     

Effect of entomopoxvirus infection of Pseudaletia separata larvae on the oviposition behavior of Cotesia kariyai

Parasitoid behavior and oviposition were monitored to investigate the ability of Cotesia kariyai (Watanabe) (Hymenoptera: Braconidae) to distinguish between entomopoxvirus-infected and noninfected larvae of Pseudaletia separata Walker (Lepidoptera: Noctuidae). Comparison of individual means revealed that searching time was not significantly different between treatments. Ovipositional time, however, differed significantly after day 8 post virus inoculation. The parasitoid adopted ovipositional posture on infected and noninfected host irrespective of the stage of infection and did not distinguish infected from noninfected larvae up to 4 days post infection. Mean number of larvae stung by the parasitoid was not influenced by the length of time interval between exposure to the virus. However, duration of ovipositor insertion was influenced by the time interval between exposure to the virus and subsequent exposure to parasitoid females. Female parasitoids did not completely reject infected larvae as unsuitable for egg deposition. However, 5 days after virus inoculation they rejected significantly more infected than noninfected larvae. Furthermore, significantly more eggs were laid in noninfected than infected larvae from day 5 following virus administration. These observations suggest that probing by Cotesia kariyai may provide information concerning host suitability.     

Are rice chromosomes components of a holocentric chromosome ancestor?

Comparative genomics reveals that cereal genomes are composed of similar genomic building blocks (linkage blocks). By stacking these blocks in a unique order, it is possible to construct a single ancestral chromosome which can be cleaved to give the basic structure of the 56 different chromosomes found in wheat, rice, maize, sorghum, millet and sugarcane. The borders of linkage blocks are defined by cereal centromeric and telomeric sites. However, a number of studies have shown that telomeric heterochromatin has neocentromeric activity, implying that linkage blocks are in fact defined by centromeric-like sites with conserved sequences. The structure of the ancestral cereal genome thus resembles a holocentric chromosome, which is the chromosome structure shared by the closest relatives of the Gramineae, the Cypericeae and Juncaceae.     

UDP-glucose:sterol glucosyltransferase: cloning and functional expression in Escherichia coli/

Steryl glucosides are characteristic lipids of plant membranes. The biosynthesis of these lipids is catalyzed by the membrane-bound UDP-glucose:sterol glucosyltransferase (EC 2.4.1.173). The purified enzyme (Warnecke and Heinz, Plant Physiol 105 (1994): 1067–1073) has been used for the cloning of a corresponding cDNA from oat (Avena sativa L.). Amino acid sequences derived from the amino terminus of the purified protein and from peptides of a trypsin digestion were used to construct oligonucleotide primers for polymerase chain reaction experiments. Screening of oat and Arabidopsis cDNA libraries with amplified labeled DNA fragments resulted in the isolation of sterol glucosyltransferase-specific cDNAs with insert lengths of ca. 2.3 kb for both plants. These cDNAs encode polypeptides of 608 (oat) and 637 (Arabidopsis) amino acid residues with molecular masses of 66 kDa and 69 kDa, respectively. The first amino acid of the purified oat protein corresponds to the amino acid 133 of the deduced polypeptide. The absence of these N-terminal amino acids reduces the molecular mass to 52 kDa, which is similar to the apparent molecular mass of 56 kDa determined for the purified protein. Different fragments of these cDNAs were expressed in Escherichia coli. Enzyme assays with homogenates of the transformed cells exhibited sterol glucosyltransferase activity.     

Foraging success of parasitoid wasps on flowers: interplay of insect morphology, floral architecture and searching behavior

Intercropping with flowering herbaceous plants increases parasitoid survivorship, fecundity and retention and pest suppression in agroecosystems. Few studies, however, have examined the compatibility of parasitoid morphology and foraging ability with floral architecture. This study shows that floral architecture influences the selection of floral host resources used to provide nutrients to parasitoids in cropping systems. Parasitoid foraging performance was evaluated using real and artificial flowers which varied in degree of nectar accessibility for two eulophid parasitoids, Edovum puttleri Grissell and Pediobius foveolatus Crawford. Comparisons were made of searching performance on artificial flowers with nectars that were either scented (made from 1:1 honey-water solution) or scentless (made from 1 m sucrose solution) and differences in head widths were compared with corolla apertures. Our results showed a disparity in the ability of E. puttleri and P. foveolatus to gain access to nectar from particular types of floral architectures. E. puttleri fed efficiently only from flowers with exposed nectaries while P. foveolatus foraged efficiently from flowers having either exposed nectaries or nectaries partially obstructed by petals and stamens. Neither wasp species could forage on flowers with cup- or tube-shaped corollas because their heads are wider than the floral apertures. E. puttleri's foraging performance decreased as nectar inaccessibility increased in the artificial flowers, while P. foveolatus' foraging performance was uniform among the different artificial flowers. This indicates that E. puttleri has less propensity to search small openings for nectar than does P. foveolatus. The foraging success of both E. puttleri and P. foveolatus on artificial flowers was lower when 1 M sucrose solution was used as an artificial nectar rather than honey-water solution, indicating that the wasps were stimulated and attracted by the nectar odor. Our systematic evaluation of floral architecture with respect to parasitoid foraging ability has enabled us to predict which types of flowers would serve as suitable floral host plants for parasitoids in the field. That is, only flowers with nectaries that are completely exposed would function as suitable floral host plants for E. puttleri, while P. foveolatus could forage on flowers with either exposed or partially exposed nectaries. Examples of potentially suitable floral hosts suggested from our study include dill (Anethum graveolens L.) and fennel (Foeniculum vulgare L.) for both E. puttleri and P. foveolatus and coriander (Coriandrum sativa L.) for P. foveolatus.     

Geranylgeranyl pyrophosphate synthase encoded by the newly isolated gene GGPS6 from Arabidopsis thaliana is localized in mitochondria

We have cloned a new geranylgeranyl pyrophosphate (GGPP) synthase gene, designated GGPS6/, from Arabidopsis thaliana genomic DNA. Nucleotide sequence analysis revealed that the GGPS6 gene contains an open reading frame coding for a protein of 343 amino acid residues with a calculated molecular mass of 37 507 Da. Also, the gene is not interrupted by an intron. The predicted amino acid sequence of the GGPS6 gene shows significant homology (34.0–57.7%) with other GGPP synthases from Arabidopsis. The GGPS6 protein contains a N-terminal signal peptide which is thought to function as an organelle targeting sequence. In fact, the GGPS6-GFP fusion protein was found to be localized exclusively in mitochondria when expressed in tobacco BY-2 cells. In vitro analysis of the enzyme activity as well as genetic complementation analysis with Erwinia uredovora crt gene cluster expressed in Escherichia coli showed that the GGPS6 gene most certainly encodes a GGPP synthase catalyzing the conversion of farnesyl pyrophosphate to GGPP.     

Overexpression of D-myo-inositol-3-phosphate synthase leads to elevated levels of inositol in Arabidopsis

In this paper, we report on the generation of transgenic Arabidopsis plants containing elevated levels of the gene product encoding the enzyme catalysing the first committed step in inositol biosynthesis, D-myo-inositol-3-phosphate (Ins3P) synthase. These plants exhibit both an increase in Ins3P synthase activity and an increase in the level of free inositol of over four-fold compared to wild-type plants. Despite these changes, we could detect no significant difference in phenotype in the transgenic plants for a number of characteristics linked with putative functions of inositol and inositol-derived metabolites. Our results indicate that the proposed engineering of inositol metabolism to generate specific plant phenotypes (e.g. salt tolerance) may require the manipulation of several genes, and that Ins3P synthase activity can be manipulated to increase the pool size of free inositol.     

Isolation,characterization and molecular cloning of a leaf-specific lectin from ramsons (Allium ursinum L.).

Lectins were isolated from roots and leaves of ramsons and compared to the previously described bulb lectins. Biochemical analyses indicated that the root lectins AUAIr and AUAIIr are identical to the bulb lectins AUAI and AUAII, whereas the leaf lectin AUAL has no counterpart in the bulbs. cDNA cloning confirmed that the leaf lectin differs from the bulb lectins. Northern blot analysis further indicated that the leaf lectin is tissue-specifically expressed. Sequence comparisons revealed that the ramsons leaf lectin differs considerably from the leaf lectins of garlic, leek, onion and shallot.     

Eucalyptus has functional equivalents of the Arabidopsis AP1 gene

Two Eucalyptus homologues of the Arabidopsis floral homeotic gene AP1 (EAP1 and EAP2/) show 60–65% homology to AP1. EAP1 and EAP2 are expressed predominantly in flower buds. EAP2 produces two different polypeptides arising from differential splicing at an intron, the shorter EAP2 protein diverging from the longer sequence after amino acid 197 and having a translation stop after residue 206. This truncated protein includes both MADS- and K-box amino acid sequences. Ectopic expression of the EAP1 or either of the two EAP2 polypeptides in Arabidopsis driven by the 35S promoter produces effects similar to the corresponding AP1 construct, causing plants to flower earlier, have shorter bolts and resemble the terminal flower mutant (tfl).     

Importance of plant size, distribution of egg masses, and weather conditions on egg parasitism of the European corn borer, Ostrinia nubilalis by Trichogramma ostriniae in sweet corn

Trichogramma ostriniae (Hym: Trichogrammatidae), an egg parasitoid of the European corn borer, Ostrinia nubilalis (Lep: Pyralidae), were released into sweet corn (Zea mays L.) fields to study the effects of weather, plant size and distribution of egg masses on egg parasitism by the wasp. Sentinel European corn borer eggs were stapled onto leaves located in the upper, middle and lower third of sweet corn plants 5 to 35 meters away from the wasp release point in either a radial or grid manner. Weather conditions and plant architecture were monitored during the experiments. Logistic regression was used to analyze the data. The results indicated that percentage of eggs parasitized was negatively related to an increase in leaf area as well as an increase in distance eggs were located from the point of release of wasps. Eggs distributed on plants at different directions from the release point received different levels of parasitism. Eggs that were stapled onto leaves in the upper third of a corn plant received much less parasitism than those on the middle and lower third of the plant. Higher mean temperature adversely affected the level of parasitism during hotter times of the season and conversely, lower temperatures (<17 °C ) reduced the egg parasitism during cooler times of the season. The longer the exposure of eggs to wasps, the higher the level of egg parasitism. However, the levels of egg parasitism for 2 day's exposure were almost the same as that for 3 day's exposure due to the limited longevity and egg-laying behavior of the wasp. These results suggest that inundative releases of T. ostriniae should be made every two to three days, with multiple release points per hectare. In addition, weather conditions and plant architecture, especially temperature, plant height and leaf area must be taken into consideration to optimize levels of parasitism.     

ABCA1和PPARγ与糖尿病动脉粥样硬化关系的研究

目的：研究ATP结合盒转运体A1（ABCA1）在多种糖尿病特有因素刺激下在巨噬细胞中的表达,以及PPARγ激动剂干预后其表达的变化,探讨ABCA1及PPARγ在糖尿病大血管并发症发展中的作用机制。从而为研究糖尿病大血管并发症的发生机制及防治提供一定的理论依据。方法：以巨噬细胞为研究对象,体外模拟糖尿病状态,分别以高葡萄糖、高胰岛素和糖基化终末产物刺激巨噬细胞,检测细胞中ABCA1表达的变化;以PPARγ激动剂预处理巨噬细胞后,再以上述因素刺激细胞,分别检测巨噬细胞中ABCA1的表达并比较。结果：高葡萄糖、高胰岛素和糖基化终末产物（AGE）可作为独立因素,导致细胞中ABCA1表达减少（P〈0.05）。PPARγ激动剂预处理后,ABCA1表达量增加（P〈0.05）。结论：糖尿病状态下,一些糖尿病特有的刺激因素如：高葡萄糖、高胰岛素和糖基化终末产物等作为独立因素使ABCA1表达减少,可能是糖尿病患者动脉粥样硬化发生率较非糖尿病人群增高的原因。PPARγ激动剂干预后,糖尿病状态下ABCA1的表达增加,这提示我们应用PPARγ激动剂可能延缓糖尿病患者动脉硬化进展。     

Characterization of Petroleum-Contaminated Soils by Thin-Layer Chromatography with Flame Ionization Detection

Petroleum hydrocarbons from 20 soils from refineries or other industrial sites were extracted with a mixture of chloroform and methanol (1:1, v/v), and the extracts were analyzed by thin layer chromatography with flame ionization detection (TLC/FID). The TLC/FID procedure has been used widely in biological and medical research but generally has been underutilized in environmental chemistry. The analysis method involved spotting a small volume of sample extract (typically 1 to 3?µl) on ten silica-coated quartz rods, and chromatographically separating constituents in the spots using solvent systems of increasing polarities (hexane, toluene, and dichloromethane + methanol). We achieved complete separation of saturated hydrocarbons, aromatic hydrocarbons, resins, and asphaltenes from the hydrocarbon-contaminated soils with this method. Analysis of the separated constituents by TLC/FID also allowed quantification of aromatic and aliphatic hydrocarbons without interference from soil biogenic lipids. A simplified version of the method permitted excellent separation of aliphatics +aromatics (forming a single peak) from resins and asphaltenes. The procedure is rapid (complete analysis of ten samples in about 1?h after extraction). Thus, the method seems well suited for synoptic surveys or screening and characterizing numerous samples prior to using more detailed and costly analyses.     

Adult feeding and lifetime reproductive success in the parasitoid Aphytis melinus

The diet of adult females of the parasitoid Aphytis melinus DeBach (Hymenoptera: Aphelinidae) includes host insects and sugar-rich foods such as nectar and honeydew. We compared the contributions of host feeding to longevity and fecundity in A. melinus females in the presence and in the absence of honey meals. First, we assessed the longevity of females that were not allowed to oviposit. While the longevity of females fed honey was significantly increased by host feeding (median ages were 30.5 days for host-fed females and 17 days for females not allowed to host feed), the lifespan of parasitoids not fed honey did not exceed 3 days for any individual and there was no effect of host feeding on longevity in this group. In the second set of experiments, we assessed the fecundity and longevity of females allowed to oviposit. We conducted two experiments, one in which honey was continuously available, and one in which honey was not available. In both experiments, daily observations were made of females that were either allowed to host feed or manually prevented from host feeding. In the presence of honey, host feeding significantly increased both fecundity and longevity, and in the absence of honey, parasitoids died within 2 days and host feeding had no significant effect on either fecundity or longevity. The lifetime fecundity of females fed honey but not hosts exceeded the initial egg complement by 60% on average. Approximately one host per day was used for host feeding whether honey was supplied or not, and each host-feeding meal contributed approximately 3.9 eggs to the lifetime fecundity of honey-fed females. In the last experiment, we compared the rate of egg resorption over a 36-h period in A. melinus females that were deprived of hosts and either fed honey or starved. While no egg resorption was detected in honey-fed females over this time period, starved females resorbed approximately 9 eggs. Thus, the availability of a sugar-rich food interacts strongly with host feeding in influencing longevity and fecundity and has a strong direct effect on egg resorption.     

Effect of entomopoxvirus infection of the smaller tea tortrix, Adoxophyes sp. on the development of the endoparasitoid, Ascogaster reticulatus

Infection of Adoxophyes sp. (Lepidoptera: Tortricidae) larvae by an entomopoxvirus (AsEPV) adversely affected the development of the endoparasitoid, Ascogaster reticulatus Watanabe (Hymenoptera: Braconidae). Parasitoid larvae developing in AsEPV-infected hosts grew more slowly and spent more time in their hosts than did parasitoid larvae developing in noninfected hosts. Percentages of emergence of larval parasitoids that developed in AsEPV-infected hosts were significantly lower than those of parasitoids that developed in noninfected hosts. Parasitoid larvae in AsEPV-infected host perished when their hosts died of AsEPV infection. Significant numbers of parasitized and infected larvae exhibited apolysis to the final instar, whereas noninfected-parasitized larvae died in the penultimate instars due to emergence of parasitoids.     

桦树松萝的石蜡切片方法改良及形态学研究

以传统石蜡切片方法为基础,在固定、软化、包埋、染色等具体方法上进行了适合松萝属植物特点的改良。结果表明:采用改良制片方法获得了染色清晰、组织完整的桦树松萝切片。桦树松萝地衣体横切面结构从外到内依次划分为皮层、藻层、髓层和中轴;皮层是由横向分裂的菌丝交织成类似于高等植物的假厚壁组织,藻层由大量共生藻的藻细胞和菌丝所组成;髓层由疏松的菌丝体组成;中轴由致密的菌丝体组成。     

The influence of clutch size on survival and reproductive potential of Hessian fly

The clutch size laid by Hessian flies (Mayetiola destructor Say) (Diptera: Cecidomyiidae) was manipulated over a range of 1 to 30 eggs on single wheat plants (Triticum aestivum, L.). Pupae developing from egg clutches were removed from plants, counted and reared through to adult eclosion. Wing lengths of adult males and females were recorded and used as an indicator of body size. Survival to pupal and adult stages, as well as mean wing length of resulting males and females, decreased as clutch size increased. Wing length of females from clutches showed a positive linear relationship with potential fecundity. The benefits of small clutches for a female Hessian fly's offspring are discussed in the context of the foraging behaviour of the ovipositing female. We predict that under high probabilities of survival and availability of host plants, females will lay smaller-sized clutches per plant. However when the probability of survival is low and host plants scare, the female will respond by laying larger-sized clutches.     

Isolation of the cDNAs encoding (+)6a-hydroxymaackiain 3-O-methyltransferase,the terminal step for the synthesis of the phytoalexin pisatin in Pisum satvium

Pisatin is the major phytoalexin produced by pea upon microbial infection. The enzyme that catalyzes the terminal step in the pisatin biosynthetic pathway is (+)6a-hydroxymaackiain 3-O-methyltransferase (HMM). We report here the isolation and characterization of two HMM cDNA clones (pHMM1 and pHMM2) made from RNA obtained from Nectria haematococca-infected pea tissue. The two clones were confirmed to encode HMM activity by heterologous expression in Escherichia coli/. The substrate specificity of the methyltransferases in E. coli was similar to the activity detected in CuCl₂-treated pea tissue. Nucleotide sequence analysis of Hmm1 and Hmm2 revealed an open reading frame of 1080 bp and 360 amino acid residues which would encode 40.36 kda and 40.41 kDa polypeptides, respectively. The deduced amino acid sequence of HMM1 has 95.8% identity to HMM2, 40.6% identity to Zrp4, a putative O-methyltransferase (OMT) in maize root, and 39.1% to pBH72-F1, a putative OMT induced in barley by fungal pathogens or UV light. Comparison of the deduced amino acid sequences of the cDNA clones to OMTs from other higher plants identified the binding sites of S-adenosylmethionine (AdoMet). Southern blot analysis showed two closely linked genes with strong homology to Hmm in the pea genome.     

Effects of previous plant infestation on sieve element acceptance by two aphids

Probing behaviour as affected by a previous infestation was studied in two aphid species on their respective host plants. Probing behaviour by Aphis fabae (reported to have beneficial effects when living in colonies) and Rhopalosiphum padi (without known beneficial effects) was studied using the electrical penetration graph (EPG) technique. In A. fabae the main effects were longer and more continuous sap ingestion, and less salivation into sieve elements before sap ingestion. These suggest phloem factors. Nevertheless, mesophyll and non-vascular tissues are likely to be involved to a lesser extent, as reflected by fewer non-probing periods before the first phloem phase on previously colonised leaves as compared to clean leaves. Total honeydew production increased on a previously colonised leaf due to the prolonged sap ingestion periods but the excretion rate was not affected, indicating that the ingestion rate remained unaltered. R. padi did not show responses to previous colonisation. It is hypothesized that the changes in probing behaviour are due to changed plant properties, chemical contents of sieve element sap and/or physiological changes induced by the saliva from the colony.