bluuebunny/crossref_metadata_2025 huggingface dataset:
Host location and selection cues in a generalist tachinid parasitoid
Authors: Stireman John O.
Published: October 2003

Tachinid flies are diverse and ecologically important insect parasitoids. However, the means by which tachinid species locate and select hosts are poorly known. Many tachinids exhibit unusually wide host ranges and they also possess well‐developed visual systems. These characteristics suggest that tachinids differ from parasitic wasps in their reliance on various sensory modes and types of cues. A series of behavioral assays using the generalist tachinid Exorista mella Walker (Diptera: Tachinidae) were conducted to examine what types of cues this parasitoid uses to locate and accept hosts, and how the cues used may reflect its ecological relationships with hosts. Female E. mella responded strongly to host motion in assays using both live hosts and host corpses, and this cue is shown to be an important elicitor of attack behavior. Females also responded to volatile chemicals associated with damaged food plants of their host in an olfactometer. Flies responded only weakly to direct visual contact with stationary hosts and odors directly associated with hosts. The behavior of female E. mella changed with experience such that more experienced flies recognized and attacked hosts more readily than did inexperienced flies. The use of general olfactory and visual cues by E. mella may be an effective strategy by this polyphagous parasitoid to locate a broad range of potential hosts.
Host selection by the heteronomous hyperparasitoid Encarsia pergandiella: multiple‐choice tests using Bemisia argentifolii as primary host
Authors: Bográn Carlos E. , Heinz Kevin M.
Published: October 2003

The ovipositional patterns of the heteronomous hyperparasitoid Encarsia pergandiella Howard (Hymenoptera: Aphelinidae) in the presence of its primary host Bemisia argentifolii Bellows & Perring (Hemiptera: Aleyrodidae), and in the presence or absence of conspecific and heterospecific secondary hosts (Encarsia formosa Gahan and Eretmocerus mundus Mercet; Hymenoptera: Aphelinidae) were examined to assess host species preferences. Host preferences by heteronomous hyperparasitoids may affect the relative abundance of co‐occurring parasitoid species and may influence host population suppression by the parasitoid community. Four combinations of hosts were tested: (1) B. argentifolii, E. mundus, and E. formosa, (2) B. argentifolii, E. formosa, and E. pergandiella, (3) B. argentifolii, E. mundus, and E. pergandiella, and, (4) B. argentifolii, E. mundus, E. formosa, and E. pergandiella. Arrays of hosts (24) were constructed in Petri dishes using leaf disks, each bearing one host. Thirty arrays of each host combination were exposed to single females for 6 h. All hosts were dissected to determine number of eggs per host. Encarsia pergandiella parasitized E. formosa hosts as frequently as E. mundus hosts. However, E. pergandiella parasitized either of these heterospecific hosts more frequently than conspecific hosts in treatments including two secondary host species. When a third parasitoid species was included in host arrays, E. pergandiella parasitized conspecific hosts as frequently as heterospecific hosts. Developmental stage of the hosts did not significantly influence host species selection by E. pergandiella. Our results indicate that host selection and oviposition by heteronomous hyperparasitoids like E. pergandiella, vary with the composition of hosts available for parasitization, and suggest a preference for heterospecific over conspecific secondary hosts.
Adaptation of a generalist moth, Operophtera brumata, to variable budburst phenology of host plants
Authors: Tikkanen Olli‐Pekka , Lyytikäinen‐Saarenmaa Päivi
Published: October 2003

The adaptation of three allopatric populations of a generalist moth, Operophtera brumata (L.), on two tree species, Prunus padus (L.) and Quercus robur (L.) which represent the extremes of the timing of budburst in spring, was studied in Finland and Sweden. The synchrony of the hatching and budbursting was monitored, and its importance to dispersal and growth of larvae was assessed by rearing cohorts of larvae, whose hatching dates were manipulated, on both hosts. In addition, the realised heritability of the hatching time was estimated.

Experimental populations hatched in approximate synchrony with the budburst of their original host species. As a result of the manipulation of the hatching dates of larvae, the growth rates of larvae decreased and the dispersal rates increased on both hosts in relation to the ageing of foliage. The realised heritability of hatching times was rather high (0.63). There were fewer differences in the host use efficiency and behaviour of the experimental populations than in the hatching phenology. The synchrony of hatching with the budburst of the local dominant host plant is probably a result of stabilising selection.
Female sex pheromone of the Chinese tortrix Cydia trasias
Authors: Fu Xiaoyan , Pan Xiangqing , Meng Xianzuo
Published: October 2003

The Chinese tortrix, Cydia trasias (Meyrick) (Lepidoptera: Tortricidae), is a major pest of the Chinese scholar‐tree (Japanese pagoda tree), Sophora japonica L.. Cydia trasias has two or three generations in Beijing, China and overwinters as larvae in seed pods, bark crevices, and twigs of the Chinese scholar‐tree (Chen, 1992; Chen & Qi, 1992). The larvae attack both petioles and seed pods. During outbreaks, the larvae can cause extensive leaf drop, bare twigs, and seed pod damage, reducing the ornamental and economic value of the tree (Enda & Yamazaki, 1987; Chen, 1992). Since the Chinese scholar‐tree is one of the most popular ornamental trees in urban and suburban areas, trees are sprayed with insecticide to control C. trasias outbreaks. Earlier field trials showed that C. trasias can be controlled by mating disruption (Zhang et al., 2001). In our early paper and patent (Fu & Meng, 1997; Meng et al., 1998), we reported E8,E10‐dodecadienyl acetate (E8,E10‐12:Ac) as a pheromone component of C. trasias, but the identification of C. trasias sex pheromone was not complete. We report here the identification and field testing of the female‐produced sex pheromone in C. trasias.
Trapping noctuid moths with synthetic floral volatile lures
Authors: Meagher Robert L.
Published: October 2003

Male and female noctuid moths were collected from plastic bucket traps that were baited with different synthetic floral chemicals and placed in peanut fields. Traps baited with phenylacetaldehyde, benzyl acetate, and a blend of phenylacetaldehyde, benzyl acetate, and benzaldehyde collected more soybean looper moths, Pseudoplusia includens (Walker), than benzaldehyde‐baited or unbaited traps. Females comprised over 67% of the moths captured and most were mated. At peak capture, over 90 male and female moths per night were collected. In another experiment, phenylacetaldehyde delivered in plastic stoppers attracted more P. includens moths than traps baited using other substrates, but this chemical delivered in wax attracted more velvetbean caterpillar moths (Anticarsia gemmatalis Hübner). Other noctuid male and female moths collected included Agrotis subterranea (F.), Argyrogramma verruca (F.), Helicoverpa zea (Boddie), and several Spodoptera species. Aculeate Hymenoptera were collected in large numbers, especially in traps baited with phenylacetaldehyde delivered from stoppers.
Food mixing strategies in the desert locust: effects of phase, distance between foods, and food nutrient content
Authors: van der Zee Brenda , Behmer Spencer T. , Simpson Stephen J.
Published: October 2003

Food mixing strategies were compared in the cryptically coloured, relatively sedentary ‘solitarious’ and the highly mobile, conspicuously coloured ‘gregarious’ phases of the desert locust, Schistocerca gregaria. Based on phase related differences in behaviour and nutritional regulatory responses, we predicted that solitarious nymphs, compared to gregarious nymphs, would move less between nutritionally complementary foods, particularly as the distance between the foods increased. We manipulated the nutritional composition [protein (p) and digestible carbohydrate (c) content] of two foods in an experimental arena and varied the distance between the foods using a factorial experimental design. Results indicated that in general, solitarious nymphs showed greater fidelity to individual food dishes than did gregarious insects (i.e., they concentrated their feeding mainly on one dish). However, results also demonstrated that for both phases fidelity to a particular food dish increased as the distance between the dishes increased, and that the number of switches between dishes decreased with increasing distance. In the smallest arenas, though, gregarious nymphs switched more frequently between the two food dishes than solitarious nymphs, even when the two dishes contained the same, near‐optimal food (p18:c24). When challenged by having the two dishes either placed furthest apart (2 m) or more divergent in nutritional composition (p29:c13 vs. p7:c35), insects of both phases regulated protein intake more strongly than carbohydrate intake, by eating more from the dish containing higher‐protein food.
Effects of constant and fluctuating temperatures on sporulation and infection by the aphid‐pathogenic fungus Pandora neoaphidis
Authors: Shah P.A. , Aebi M. , Tuor U.
Published: October 2003

Laboratory studies were performed to assess the importance of temperature on sporulation and infection by the aphid‐pathogenic fungus Pandora neoaphidis (Remaudière and Hennebert) Humber. Numbers of primary conidia discharged from mycelium formulated as alginate granules and unformulated mycelial mats were assessed, as well as infection of the potato aphid, Macrosiphum euphorbiae (Thomas) (Homoptera, Hemiptera, Aphididae), using culture plugs as inoculum sources. Sporulation from experiments at constant temperatures indicated the optimum temperature range was 10–20 °C for both mycelial preparations and there was no or very little sporulation at 30 °C. Infection of aphids kept at 15 °C was 34–50%, while infection at 25 °C was 11–44%. At 20 °C, 77–79% of aphids were infected. Under fluctuating temperature cycles, conidia numbers did not differ when mycelial preparations were maintained at 18–25 °C compared with 18–20 °C, but fewer conidia were recorded when preparations were exposed continuously to 18–30 °C. Infections of inoculated aphids kept for varying numbers of days at 18–25 °C varied between 24–47%, but only 3–32% of aphids were infected when exposed to a cycle of 18–30 °C for various times. Unformulated mycelial mats of P. neoaphidis appear to be superior to forumlated alginate granules for use in experimental greenhouse and field trials, since temperature stability is similar for both materials but mycelial mats are much easier to produce.
Costs of secondary parasitism in the facultative hyperparasitoid Pachycrepoideus dubius: does host size matter?
Authors: Grandgirard Julie , Poinsot Denis , Krespi Liliane , Nénon Jean‐Pierre , Cortesero Anne‐Marie
Published: October 2003

Although hyperparasitism frequently occur in parasitic insects, many aspects of this strategy remain unknown. We investigated possible fitness costs of hyperparasitism as influenced by host size. Our study was conducted with the facultative hyperparasitoid Pachycrepoideus dubius Ashmead (Hymenoptera: Pteromalidae), which parasitizes host species differing greatly in size. We compared some fitness traits (level of successful parasitism, development time, sex ratio and offspring size) of P. dubius developing on large secondary/primary (Delia radicum L. (Diptera: Anthomyiidae)/Trybliographa rapae Westwood (Hymenoptera: Figitidae)) or small secondary/primary host species (Drosophila melanogaster L./Asobara tabida Nees (Hymenoptera: Braconidae)). In no‐choice and choice experiments, P. dubius was able to develop on different stages of T. rapae (L2 (endophagous), L4 (ectophagous), and pupae) but that it preferred to parasitize unparasitized D. radicum pupae over pupae parasitized by T. rapae. Furthermore, in P. dubius, hyperparasitism was associated with fitness costs (lower level of successful parasitism, smaller adult size) and these costs were greater on the smallest host complex. We hypothesize that the size of D. melanogaster pupae parasitized by A. tabida may be close to the suboptimal host size for P. dubius beneath which the costs of hyperparasitism make this strategy nonadaptive. Hyperparasitism in terms of trade‐offs between host quality and abundance of competitors is discussed.
The chemical world of crucivores: lures, treats and traps
Authors: Renwick J. Alan A.
Published: October 2003

The host ranges of several insects that are specialists on crucifers (Brassicaceae) are closely linked to the presence of glucosinolates in these plants. These glycosides often serve as stimulants for oviposition and/or feeding, while their volatile hydrolysis products may be attractants for several species. However, many crucifers produce additional secondary compounds that act as repellents, deterrents or toxins, which protect them from these insects. The widely different responses of the various crucifer specialists to these compounds reflect different degrees of adaptation to the plant defenses. Thus native insects are often unable to survive on introduced plants, although the ubiquitous glucosinolates may trigger oviposition ‘mistakes’. The success of highly invasive cruciferous weeds may be due in part to a lack of local herbivore adaptation to unique chemical constituents of these plants. However, the concentrations of secondary chemicals vary with season, environmental conditions, and geographical location. This could mean that windows of opportunity exist for utilization of introduced plants. Recent studies with garlic mustard, Alliaria petiolata, and wintercress, Barbarea vulgaris, in the USA have shown that these introduced plants are resistant to the native butterfly, Pieris napi oleracea. The combined effects of a flavone glycoside and a unique butenenitrile glycoside in the garlic mustard appear to be responsible for blocking feeding by this insect. Barbarea vulgaris is also resistant to the diamondback moth, Plutella xylostella, in North America and to the flea beetle, Phyllotreta nemorum, in Europe. Comparative studies indicate that common resistance mechanisms are involved and bioassays have been developed to elucidate the chemical nature of this resistance.
Host specificity and host recognition in a chemically‐defended herbivore, the tenthredinid sawfly Rhadinoceraea nodicornis
Authors: Barker Alison , Schaffner Urs , Boevé Jean‐Luc
Published: October 2003

The sawfly Rhadinoceraea nodicornis Konow (Hymenoptera: Tenthredinidae) is a member of a closely related group of species, the tribe Phymatocerini, which feed on the Liliales and Ranunculales. It is known to sequester steroid alkaloids from its host plants, species in the genus Veratrum (Liliales: Melanthiaceae), and to use them as a defence against predators. There are known chemical relationships between the hosts of R. nodicornis and hosts of related sawfly species. We tested whether the R. nodicornis larvae would accept hosts of closely‐ and more distantly‐related sawflies, but found that they accepted only plant species in the genus Veratrum. This specificity was apparently innate, as it was independent of early larval experience. A feeding bioassay showed that the steroid alkaloids from Veratrum nigrum were phagostimulatory for R. nodicornis larvae, suggesting that they may be involved in host recognition. We discuss the possibility that the evolution of recognition of specific compounds may represent the mechanism of host radiation within the Phymatocerini.
Incidence of apple fruit and leaf surface metabolites on Cydia pomonella oviposition
Authors: Lombarkia Nadia , Derridj Sylvie
Published: October 2003

Water soluble metabolites identified from surfaces of apple tree fruit and leaf stimulate oviposition in Cydia pomonella L. The effects of two artificial blends of primary metabolites representing fruit and leaf surfaces, respectively, and of components within the blends were examined on egg‐laying after two time periods: 3 min and 25 min of darkness. An artificial mixture of six metabolites, viz., three sugar alcohols (sorbitol, quebrachitol, and myo‐inositol) and three sugars (glucose, fructose, and sucrose) did stimulate egg‐laying. Fructose, sorbitol, and myo‐inositol are important components of the stimulatory blend. Contact durations may induce variations in egg‐laying responses. After 3 min of darkness, there were no differences in numbers of females laying eggs nor in the numbers of eggs laid on cloths treated with the complete blends and the controls. There were, however, clear effects of groups of compounds and of individual compounds. Reduced blends without sugars and sugar alcohols were in many cases significantly less stimulatory than the complete blends and the controls. After 25 min of darkness, the proportions of females laying eggs as well as the numbers of eggs were higher after treatment with the complete blends than on the controls. The proportions of females laying eggs on cloths treated with the reduced blends were rather similar to the controls, whereas there were still significant effects on the numbers of eggs laid after treatment with reduced blends derived from fruits but not from leaves.
Xylem ingestion by winged aphids
Authors: Powell Glen , Hardie Jim
Published: October 2003

When aphids and their host plant are incorporated in a DC electrical circuit, phloem and xylem ingestion register as separate waveforms of the electrical penetration graph (EPG) signal. Aphids are primarily phloem feeders; xylem ingestion is seldom reported but can be induced experimentally by fasting the insects in desiccating conditions. In experiments with the black bean aphid, Aphis fabae Scop., young winged (alate) and unwinged (apterous) virginoparous adults were collected from their natal host plants (broad bean, Vicia faba L.) and allowed 3‐h continuous EPG‐recorded access to V. faba seedlings. Several aphids (47% of both morphs) showed ingestion from phloem sieve elements. Alate aphids also showed frequent xylem ingestion (60% of individuals), but no apterous aphids exhibited this activity. The EPG technique involves attachment of a fine gold wire electrode to each insect, a process that may affect normal behaviour at the plant surface. However, when the technique was modified to monitor the stylet activities of freely‐settled aphids, high levels of xylem ingestion by alates were also recorded. The results suggest that the developmental physiology of winged aphids somehow predisposes them to xylem ingestion, possibly as a result of dehydration during the teneral period. Alate aphids may reduce their weight by fasting before take‐off, giving aerodynamic benefits, but making rehydration, via xylem uptake, a priority following plant contact.
The effect of different plant nutrient regimes on the aphid Macrosiphum euphorbiae growing on petunia
Authors: Jansson Johanna , Ekbom Barbara
Published: October 2003

Three experiments were conducted to study how nutrient content of the host plant, Petunia axillaris hybrida Villm. Grandiflora Group, affects the performance of Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae). Aphid performance was analysed in relation to plant nutrient levels and the ratio of nitrogen to potassium (N/K). Phosphorus (P) had a positive effect on several parameters of aphid performance. Both P and K were associated with a short development time but a strong correlation between P and K content made it impossible to detect their relative importance. In one experiment aphid performance was significantly lower on unfertilised plants with low N content, suggesting a positive effect of N. A high N/K ratio did not, in general, increase aphid performance. The complexity of plant nutrient content on aphid performance suggests that not only nutrient levels but also ratios of nutrients must be considered.
Do fecal shields provide physical protection to larvae of the tortoise beetles Plagiometriona flavescens and Stolas chalybea against natural enemies?
Authors: Nogueira‐de‐Sá Flávia , Trigo José Roberto
Published: October 2003

During their larval phase, Plagiometriona flavescens (Boheman, 1855) and Stolas chalybea (Germar, 1824) (Chrysomelidae: Cassidinae), carry masses of feces and exuviae on their back called fecal shield, and it is suggested to protect larvae against natural enemies. We investigated if the physical barrier provided by the shield plays any role in the defense of these larvae. We conducted a field experiment checking the mortality of larvae of both species with their natural shields substituted by an artificial shield, with shields removed and with their shields intact. Mortality controls for each of the 3 shield treatments were carried out on host plants protected against natural enemies. On both species we observed that larvae with their shields intact had a significant lower mortality proportion than larvae with artificial shields or without shields. Control larvae on protected plants had low mortality. Our results agree with literature data, showing that fecal shields do not provide a physical protection to larvae but are important in their defense, probably due to the chemicals present in them.
Evaluation of dietary effects of transgenic corn pollen expressing Cry3Bb1 protein on a non‐target ladybird beetle, Coleomegilla maculata
Authors: Duan Jian J. , Head Graham , McKee Michael J. , Nickson Thomas E. , Martin John W. , Sayegh Fouad S.
Published: October 2003

A transgenic corn event (MON 863) has been recently developed by Monsanto Company for control of corn rootworms, Diabrotica spp. (Coleoptera: Chrysomelidae). This transgenic corn event expresses the cry3Bb1 gene derived from Bacillus thuringiensis (Berliner), which encodes the insecticidal Cry3Bb1 protein for corn rootworm control. A continuous feeding study was conducted in the laboratory to evaluate the dietary effect of MON 863 pollen expressing the Cry3Bb1 protein on the survival, larval development, and reproductive capacity of the non‐target species, Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae). First instar C. maculata (less than 24 h old) and newly emerging adults (less than 72 h old) were fed individually on a diet mixture containing 50% of MON 863 pollen, non‐transgenic (control) corn pollen, bee pollen (a component of normal rearing diet), or potassium arsenate‐treated control corn pollen. In the larval tests, 96.7%, 90.0%, and 93.3% of C. maculata larvae successfully pupated and then emerged as adults when fed on MON 863 pollen, non‐transgenic corn pollen, and bee pollen (normal rearing) diets, respectively. Among the larvae completing their development, there were no significant differences in the developmental time to pupation and adult emergence among the transgenic corn pollen, non‐transgenic corn pollen, and bee pollen diet treatments. All larvae fed on arsenate treated corn pollen diet died as larvae. For tests with adults, 83.3%, 80.0%, and 100% of adult C. maculata survived for the 30 days of the test period when reared on diets containing 50% of MON 863 pollen, non‐transgenic corn pollen, and bee pollen respectively. While the adult survival rate on MON 863 pollen diet was significantly less than that on the bee pollen diet, there was no significant difference between the MON 863 and non‐transgenic corn pollen treatments. During the period of adult testing, an average of 77, 80, and 89 eggs per female were laid by females fed on the MON 863 pollen, control corn pollen, and bee pollen, respectively; no significant differences were detected in the number of eggs laid among these treatments. These results demonstrate that when offered at 50% by weight of the dietary component, transgenic corn (MON 863) pollen expressing Cry3Bb1 protein had no measurable negative effect on the survival and development of C. maculata larvae to pupation and adulthood nor any adverse effect on adult survival and reproductive capacity. Relevance of these findings to ecological impacts of transgenic Bt crops on non‐target beneficial insects is discussed.
Increase in cereal stem borer populations through partial elimination of natural enemies
Authors: Kfir Rami
Published: October 2003

An insecticide exclusion method was used to evaluate the effect of parasitoids on level of infestation by the stem borers, Busseola fusca (Fuller) and Chilo partellus (Swinhoe), in grain sorghum. In field trials conducted at Brits and at Delmas, South Africa, a selective organophosphate insecticide, dimethoate, was applied twice weekly at each site to three subplots whereas three other identical subplots served as controls. Twelve plants were randomly selected from each subplot at weekly intervals and removed from the field. In the laboratory all plants were dissected to record borer infestation. In order to determine parasitism levels egg batches were kept in Petri dishes and all borer larvae and pupae were kept individually in vials until either parasitoids or moths emerged. At Brits ca. 97% of borers were C. partellus and 3% B. fusca, whereas at Delmas 37.5% were C. partellus and 62.5% B. fusca. The most abundant parasitoids of B. fusca were Cotesia sesamiae (Cameron) and Bracon sesamiae Cameron. The dominant parasitoids of C. partellus at both sites were C. sesamiae, Stenobracon spec., Dentichasmias busseolae Henrich and Pediobius furvus (Gahan). No egg parasitoids were found. At both sites, infestation levels in the sprayed plots were significantly higher than in the untreated plots. On the other hand, parasitism levels of borers in the unsprayed plots were significantly higher than in the treated plots. It was concluded that the higher infestation level of sorghum by stem borers in the sprayed plots was because of partial elimination of parasitoids and possibly other natural enemies by the pesticide.
Influence of pollen origin on performance of Bombus terrestris micro‐colonies
Authors: Génissel A. , Aupinel P. , Bressac C. , Tasei J.‐N. , Chevrier C.
Published: October 2003

The effect of the floral origin of pollen on the reproductive success of Bombus terrestris Latrum bumblebee (Apidae: Bombinae), was investigated by feeding micro‐colonies of queenless workers with different pollen types. We used a commercial pollen blend and three unifloral pollens, Prunus, Salix, and Taraxacum. Among the unifloral pollens, pollen quality did not influence egg production, but did influence egg laying delay and larval growth. The quality of pollens varied according to their protein content and protein efficacy (PE). Pollen from Prunus (27.5% w/w protein, PE = 10) resulted in the largest number of progeny, whereas Taraxacum (17.2% w/w protein, PE = 0) did not result in any offspring, due to high oophagy and larval ejection. Salix (20% w/w protein) and the blend (222.8% protein) diets gave rise to intermediate reproductive outputs. When pollen quality was sufficient for larval growth, the fitness of the male offspring was not affected over the range of the experimental diets. Our results suggest that quantitative and qualitative variations of pollen proteins have considerable influence on the reproductive success of bumblebees. Furthermore, larval growth has specific nutritive demands not provided by Taraxacum pollen, which is missing two essential amino acids.
Phospholipid composition and pheromonal activity of nuptial secretion of the male German cockroach, Blattella germanica
Authors: Kugimiya Soichi , Nishida Ritsuo , Kuwahara Yasumasa , Sakuma Masayuki
Published: October 2003

As a part of the sequential courtship behavior of the German cockroach, Blattella germanica, females feed on the nuptial secretion from the male tergal glands. The pheromonal secretion, consisting mainly of oligosaccharides and phospholipids, strongly elicits a feeding response in virgin females. The phospholipids were composed of phosphatidylethanolamine and phosphatidylcholine. Their fatty acid compositions were determined by chromatographic and enzymatic methods. Although an authentic blend of phospholipids (1,2‐dioleoylphosphatidylethanolamine and 1,2‐dioleoylphosphatidylcholine) showed a marginal phagostimulant activity, addition of the blend to an authentic blend of oligosaccharides (maltose and maltotriose) strongly enhanced the activity to nearly the level of the crude extract. These results indicate that the nuptial feeding behavior is elicited by a synergistic action between phospholipids and oligosaccharides.
A complex history of rearrangement in an orthologous region of the maize, sorghum, and rice genomes
Authors: Ilic Katica , SanMiguel Phillip J. , Bennetzen Jeffrey L.
Published: October 2003

The sequences of large insert clones containing genomic DNA that is orthologous to the maize
adh1
region were obtained for sorghum, rice, and the
adh1
-homoeologous region of maize, a remnant of the tetraploid history of the
Zea
lineage. By using all four genomes, it was possible to describe the nature, timing, and lineages of most of the genic rearrangements that have differentiated this chromosome segment over the last 60 million years. The rice genome has been the most stable, sharing 11 orthologous genes with sorghum and exhibiting only one tandem duplication of a gene in this region. The lineage that gave rise to sorghum and maize acquired a two-gene insertion (containing the
adh
locus), whereas sorghum received two additional gene insertions after its divergence from a common ancestor with maize. The two homoeologous regions of maize have been particularly unstable, with complete or partial deletion of three genes from one segment and four genes from the other segment. As a result, the region now contains only one duplicated locus compared with the eight original loci that were present in each diploid progenitor. Deletion of these maize genes did not remove both copies of any locus. This study suggests that grass genomes are generally unstable in local genome organization and gene content, but that some lineages are much more unstable than others. Maize, probably because of its polyploid origin, has exhibited extensive gene loss so that it is now approaching a diploid state.
Transition-path sampling of β-hairpin folding
Authors: Bolhuis Peter G.
Published: October 2003

We examine the dynamical folding pathways of the C-terminal β-hairpin of protein G-B1 in explicit solvent at room temperature by means of a transition-path sampling algorithm. In agreement with previous free-energy calculations, the resulting path ensembles reveal a folding mechanism in which the hydrophobic residues collapse first followed by backbone hydrogen-bond formation, starting with the hydrogen bonds inside the hydrophobic core. In addition, the path ensembles contain information on the folding kinetics, including solvent motion. Using the recently developed transition interface sampling technique, we calculate the rate constant for unfolding of the protein fragment and find it to be in reasonable agreement with experiments. The results support the validation of using all-atom force fields to study protein folding.
Systemic and cell type-specific gene expression patterns in scleroderma skin
Authors: Whitfield Michael L. , Finlay Deborah R. , Murray John Isaac , Troyanskaya Olga G. , Chi Jen-Tsan , Pergamenschikov Alexander , McCalmont Timothy H. , Brown Patrick O. , Botstein David , Connolly M. Kari
Published: October 2003

We used DNA microarrays representing >12,000 human genes to characterize gene expression patterns in skin biopsies from individuals with a diagnosis of systemic sclerosis with diffuse scleroderma. We found consistent differences in the patterns of gene expression between skin biopsies from individuals with scleroderma and those from normal, unaffected individuals. The biopsies from affected individuals showed nearly indistinguishable patterns of gene expression in clinically affected and clinically unaffected tissue, even though these were clearly distinguishable from the patterns found in similar tissue from unaffected individuals. Genes characteristically expressed in endothelial cells, B lymphocytes, and fibroblasts showed differential expression between scleroderma and normal biopsies. Analysis of lymphocyte populations in scleroderma skin biopsies by immunohistochemistry suggest the B lymphocyte signature observed on our arrays is from CD20
+
B cells. These results provide evidence that scleroderma has systemic manifestations that affect multiple cell types and suggests genes that could be used as potential markers for the disease.
Evolution of olfactory receptor genes in the human genome
Authors: Niimura Yoshihito , Nei Masatoshi
Published: October 2003

Olfactory receptor (OR) genes form the largest known multigene family in the human genome. To obtain some insight into their evolutionary history, we have identified the complete set of OR genes and their chromosomal locations from the latest human genome sequences. We detected 388 potentially functional genes that have intact ORFs and 414 apparent pseudogenes. The number and the fraction (48%) of functional genes are considerably larger than the ones previously reported. The human OR genes can clearly be divided into class I and class II genes, as was previously noted. Our phylogenetic analysis has shown that the class II OR genes can further be classified into 19 phylogenetic clades supported by high bootstrap values. We have also found that there are many tandem arrays of OR genes that are phylogenetically closely related. These genes appear to have been generated by tandem gene duplication. However, the relationships between genomic clusters and phylogenetic clades are very complicated. There are a substantial number of cases in which the genes in the same phylogenetic clade are located on different chromosomal regions. In addition, OR genes belonging to distantly related phylogenetic clades are sometimes located very closely in a chromosomal region and form a tight genomic cluster. These observations can be explained by the assumption that several chromosomal rearrangements have occurred at the regions of OR gene clusters and the OR genes contained in different genomic clusters are shuffled.
The primary mechanism of attenuation of bacillus Calmette–Guérin is a loss of secreted lytic function required for invasion of lung interstitial tissue
Authors: Hsu Tsungda , Hingley-Wilson Suzanne M. , Chen Bing , Chen Mei , Dai Annie Z. , Morin Paul M. , Marks Carolyn B. , Padiyar Jeevan , Goulding Celia , Gingery Mari , Eisenberg David , Russell Robert G. , Derrick Steven C. , Collins Frank M. , Morris Sheldon L. , King C. Harold , Jacobs William R.
Published: October 2003

Tuberculosis remains a leading cause of death worldwide, despite the availability of effective chemotherapy and a vaccine. Bacillus Calmette–Guérin (BCG), the tuberculosis vaccine, is an attenuated mutant of
Mycobacterium bovis
that was isolated after serial subcultures, yet the functional basis for this attenuation has never been elucidated. A single region (
RD1
), which is absent in all BCG substrains, was deleted from virulent
M. bovis
and
Mycobacterium tuberculosis
strains, and the resulting Δ
RD1
mutants were significantly attenuated for virulence in both immunocompromised and immunocompetent mice. The
M. tuberculosis
Δ
RD1
mutants were also shown to protect mice against aerosol challenge, in a similar manner to BCG. Interestingly, the Δ
RD1
mutants failed to cause cytolysis of pneumocytes, a phenotype that had been previously used to distinguish virulent
M. tuberculosis
from BCG. A specific transposon mutation, which disrupts the
Rv3874 Rv3875
(
cfp-10 esat-6
) operon of
RD1
, also caused loss of the cytolytic phenotype in both pneumocytes and macrophages. This mutation resulted in the attenuation of virulence in mice, as the result of reduced tissue invasiveness. Moreover, specific deletion of each transcriptional unit of
RD1
revealed that three independent transcriptional units are required for virulence, two of which are involved in the secretion of ESAT-6 (6-kDa early secretory antigenic target). We conclude that the primary attenuating mechanism of bacillus Calmette–Guérin is the loss of cytolytic activity mediated by secreted ESAT-6, which results in reduced tissue invasiveness.
Extensive regional atmospheric hydrocarbon pollution in the southwestern United States
Authors: Katzenstein Aaron S. , Doezema Lambert A. , Simpson Isobel J. , Blake Donald R. , Rowland F. Sherwood
Published: October 2003

Light alkane hydrocarbons are present in major quantities in the near-surface atmosphere of Texas, Oklahoma, and Kansas during both autumn and spring seasons. In spring 2002, maximum mixing ratios of ethane [34 parts per 10
9
by volume (ppbv)], propane (20 ppbv), and
n
-butane (13 ppbv) were observed in north-central Texas. The elevated alkane mixing ratios are attributed to emissions from the oil and natural gas industry. Measured alkyl nitrate mixing ratios were comparable to urban smog values, indicating active photochemistry in the presence of nitrogen oxides, and therefore with abundant formation of tropospheric ozone. We estimate that 4–6 teragrams of methane are released annually within the region and represents a significant fraction of the estimated total U.S. emissions. This result suggests that total U.S. natural gas emissions may have been underestimated. Annual ethane emissions from the study region are estimated to be 0.3–0.5 teragrams.
Origins of mitochondrial thymidine triphosphate: Dynamic relations to cytosolic pools
Authors: Pontarin Giovanna , Gallinaro Lisa , Ferraro Paola , Reichard Peter , Bianchi Vera
Published: October 2003

Nuclear and mitochondrial (mt) DNA replication occur within two physically separated compartments and on different time scales. Both require a balanced supply of dNTPs. During S phase, dNTPs for nuclear DNA are synthesized
de novo
from ribonucleotides and by salvage of thymidine in the cytosol. Mitochondria contain specific kinases for salvage of deoxyribonucleosides that may provide a compartmentalized synthesis of dNTPs. Here we investigate the source of intra-mt thymidine phosphates and their relationship to cytosolic pools by isotope-flow experiments with [
3
H]thymidine in cultured human and mouse cells by using a rapid method for the clean separation of mt and cytosolic dNTPs. In the absence of the cytosolic thymidine kinase, the cells (
i
) phosphorylate labeled thymidine exclusively by the intra-mt kinase, (
ii
) export thymidine phosphates rapidly to the cytosol, and (
iii
) use the labeled dTTP for nuclear DNA synthesis. The specific radioactivity of dTTP is highly diluted, suggesting that cytosolic
de novo
synthesis is the major source of mt dTTP. In the presence of cytosolic thymidine kinase dilution is 100-fold less, and mitochondria contain dTTP with high specific radioactivity. The rapid mixing of the cytosolic and mt pools was not expected from earlier data. We propose that in proliferating cells dNTPs for mtDNA come largely from import of cytosolic nucleotides, whereas intra-mt salvage of deoxyribonucleosides provides dNTPs in resting cells. Our results are relevant for an understanding of certain genetic mitochondrial diseases.
Visual cortex is rescued from the effects of dark rearing by overexpression of BDNF
Authors: Gianfranceschi Laura , Siciliano Rosita , Walls Jennifer , Morales Bernardo , Kirkwood Alfredo , Huang Z. Josh , Tonegawa Susumu , Maffei Lamberto
Published: October 2003

Visual deprivation such as dark rearing (DR) prolongs the critical period for ocular dominance plasticity and retards the maturation of γ-aminobutyric acid (GABA)ergic inhibition in visual cortex. The molecular signals that mediate the effects of DR on the development of visual cortex are not well defined. To test the role of brain-derived neurotrophic factor (BDNF), we examined the effects of DR in transgenic mice in which BDNF expression in visual cortex was uncoupled from visual experience and remained elevated during DR. In dark-reared transgenic mice, visual acuity, receptive field size of visual cortical neurons, critical period for ocular dominance plasticity, and intracortical inhibition were indistinguishable from those observed in light-reared mice. Therefore, BDNF overexpression is sufficient for the development of aspects of visual cortex in the absence of visual experience. These results suggest that reduced BDNF expression contributes to retarded maturation of GABAergic inhibition and delayed development of visual cortex during visual deprivation.
HdmX stimulates Hdm2-mediated ubiquitination and degradation of p53
Authors: Linares Laëtitia K. , Hengstermann Arnd , Ciechanover Aaron , Müller Stefan , Scheffner Martin
Published: October 2003

The RING finger proteins HdmX and Hdm2 share significant structural and functional similarity. Hdm2 is a member of the RING finger family of ubiquitin-protein ligases E3 and targets the tumor suppressor protein p53 for degradation. Although HdmX also binds to p53, HdmX does not induce p53 degradation. Moreover, HdmX has been reported to interfere with p53 degradation in overexpression experiments. To obtain insight into the mechanism by which HdmX interferes with p53 degradation, we studied the effect of HdmX on the E3 activity of Hdm2
in vitro
. Surprisingly, this revealed that HdmX stimulates Hdm2-mediated ubiquitination of p53 and that HdmX facilitates ubiquitination of Hdm2 and vice versa. In addition, down-regulation of HdmX expression within cells results in the accumulation of both p53 and Hdm2. Because HdmX alone does not have appreciable E3 activity, these data indicate that HdmX acts as a stimulator, rather than as an inhibitor, of the E3 activity of Hdm2 and that, at least under certain conditions, HdmX is actively involved in the degradation of both p53 and Hdm2.
Protein complexes and functional modules in molecular networks
Authors: Spirin Victor , Mirny Leonid A.
Published: October 2003

Proteins, nucleic acids, and small molecules form a dense network of molecular interactions in a cell. Molecules are nodes of this network, and the interactions between them are edges. The architecture of molecular networks can reveal important principles of cellular organization and function, similarly to the way that protein structure tells us about the function and organization of a protein. Computational analysis of molecular networks has been primarily concerned with node degree [Wagner, A. & Fell, D. A. (2001)
Proc. R. Soc. London Ser. B
268, 1803–1810; Jeong, H., Tombor, B., Albert, R., Oltvai, Z. N. & Barabasi, A. L. (2000)
Nature
407, 651–654] or degree correlation [Maslov, S. & Sneppen, K. (2002)
Science
296, 910–913], and hence focused on
single
/
two-body
properties of these networks. Here, by analyzing the
multibody
structure of the network of protein–protein interactions, we discovered molecular modules that are densely connected within themselves but sparsely connected with the rest of the network. Comparison with experimental data and functional annotation of genes showed two types of modules: (
i
) protein complexes (splicing machinery, transcription factors, etc.) and (
ii
) dynamic functional units (signaling cascades, cell-cycle regulation, etc.). Discovered modules are highly statistically significant, as is evident from comparison with random graphs, and are robust to noise in the data. Our results provide strong support for the network modularity principle introduced by Hartwell
et al.
[Hartwell, L. H., Hopfield, J. J., Leibler, S. & Murray, A. W. (1999)
Nature
402, C47–C52], suggesting that found modules constitute the “building blocks” of molecular networks.
Invasion-inhibitory antibodies inhibit proteolytic processing of apical membrane antigen 1 ofPlasmodium falciparummerozoites
Authors: Dutta Sheetij , Haynes J. David , Moch J. Kathleen , Barbosa Arnoldo , Lanar David E.
Published: October 2003

Apical membrane antigen 1 (AMA-1) is a promising vaccine candidate forPlasmodium falciparummalaria. Antibodies against AMA-1 ofP. falciparum(PfAMA-1) interrupt merozoite invasion into RBCs. Initially localized within the apical complex, PfAMA-1 is proteolytically processed and redistributed circumferentially on merozoites at about the time of their release and invasion into RBCs. An 83-kDa precursor form of PfAMA-1 is processed to 66-kDa and then to 48- and 44-kDa products. We show that, even at low concentrations, IgG antibodies against correctly folded recombinant PfAMA-1 cross-linked and trapped the 52-, 48-, and 44-kDa proteolytic products on merozoites. These products are normally shed into the culture medium. At higher concentrations antibodies inhibited invasion into RBCs and caused a reduction in the amount of 44- and 48-kDa products, both on merozoites and in the culture medium. A corresponding increase also occurred in the amount of the 66- and 52-kDa forms detected on the merozoites. These antibodies also prevented circumferential redistribution of AMA-1. In contrast, monovalent invasion-inhibitory Fab fragments caused accumulation of 66- and 52-kDa forms, with no cross-linking, trapping, or prevention of redistribution. Antibodies at low concentrations can be used as trapping agents for intermediate and soluble forms of AMA-1 and are useful for studying proteolytic processing of AMA-1. With this technique, it was confirmed that protease inhibitor chymostatin and Ca2+chelators can inhibit the breakdown of the 66-kDa form. We propose that antibodies to AMA-1 capable of inhibiting erythrocyte invasion act by disrupting proteolytic processing of AMA-1.
Soluble CD40 ligand induces β
3
integrin tyrosine phosphorylation and triggers platelet activation by outside-in signaling
Authors: Prasad K. S. Srinivasa , Andre Patrick , He Ming , Bao Ming , Manganello Jeanne , Phillips David R.
Published: October 2003

We earlier reported that the soluble form of the CD40 ligand (sCD40L), is involved in thrombosis by stabilizing platelet thrombi. In this article, we have determined the mechanism by which this protein affects platelet biology. Addition of sCD40L to washed platelets was found to activate the receptor function of α
IIb
β
3
as measured by the induction of fibrinogen binding and the formation of platelet microparticles. Mutation in the KGD sequence (D117E) of sCD40L, the α
IIb
β
3
-binding domain in the N terminus of the protein resulted in a loss of the platelet-stimulatory activity of this protein. Integrilin, a α
IIb
β
3
antagonist, but not an antibody to CD40 that blocked the ligand-binding activity, inhibited these platelet-stimulatory events. CD40
-/-
platelets bound fibrinogen and formed microparticles similar to WT platelets, again indicating that CD40 is not involved in sCD40L-induced platelet activation. Exposure of platelets to sCD40L, but not D117E-sCD40L-coated surfaces, induced platelet thrombi formation under arterial shear rate. sCD40L-induced platelet stimulation resulted in the phosphorylation of tyrosine-759 in the cytoplasmic domain of β
3
. Platelets from the diYF mouse strain, expressing β
3
in which both cytoplasmic tyrosines are mutated to phenylalanine, were defective in sCD40L-induced platelet stimulation. These data indicate that sCD40L is a primary platelet agonist and that platelet stimulation is induced by the binding of the KGD domain of sCD40L to α
IIb
β
3
, triggering outside-in signaling by tyrosine phosphorylation of β
3
.