Induced tolerance to abiotic and biotic stresses of broccoli and Arabidopsis after treatment with elicitor molecules.

The plant hormones salicylic acid (SA) and jasmonic acid (JA) regulate defense mechanisms capable of overcoming different plant stress conditions and constitute distinct but interconnected signaling pathways. Interestingly, several other molecules are reported to trigger stress-specific defense responses to biotic and abiotic stresses. In this study, we investigated the effect of 14 elicitors against diverse but pivotal types of abiotic (drought) and biotic (the chewing insect Ascia monuste, the hemibiotrophic bacterium Pseudomonas syringae DC 3000 and the necrotrophic fungus Alternaria alternata) stresses on broccoli and Arabidopsis. Among the main findings, broccoli pre-treated with SA and chitosan showed the highest drought stress recovery in a dose-dependent manner. Several molecules led to increased drought tolerance over a period of three weeks. The enhanced drought tolerance after triggering the SA pathway was associated with stomata control. Moreover, methyl jasmonate (MeJA) reduced A. monuste insect development and plant damage, but unexpectedly, other elicitors increased both parameters. GUS reporter assays indicated expression of the SA-dependent PR1 gene in plants treated with nine elicitors, whereas the JA-dependent LOX2 gene was only expressed upon MeJA treatment. Overall, elicitors capable of tackling drought and biotrophic pathogens mainly triggered the SA pathway, but adversely also induced systemic susceptibility to chewing insects. These findings provide directions for potential future in-depth characterization and utilization of elicitors and induced resistance in plant protection.

Effects of Host Interspecific Interaction in the Maculinea-Myrmica Parasite-Host System.

A model of interspecific host competition in a system with one parasite (butterfly-Maculinea) and multiple potential hosts (ants-Myrmica) is presented. Results indicate that host interspecific competition increases the occurrence of multiple host behaviour in Maculinea natural populations but decreases the ability of the parasite populations to adapt to the most abundant host species. These qualitative predictions were compared with data on host specificity, with good agreement. Analysis of the data also indicates that Maculinea teleius and Maculinea arion respond differently to changes in relative host abundances. Maculinea teleius shows a larger fraction of sites where it displays multiple host behaviour and a larger fraction of sites where the niches of the hosts overlap. In some instances, Maculinea teleius is adapted to Myrmica hosts that are present in lower frequencies. Maculinea arion is locally more host-specific and occurs at sites where host interspecific competition is unlikely and is more frequently adapted to the most abundant host species.

Wounding of Arabidopsis halleri leaves enhances cadmium accumulation that acts as a defense against herbivory.

Approximately 0.2% of all angiosperms are classified as metal hyperaccumulators based on their extraordinarily high leaf metal contents, for example >1% zinc, >0.1% nickel or >0.01% cadmium (Cd) in dry biomass. So far, metal hyperaccumulation has been considered to be a taxon-wide, constitutively expressed trait, the extent of which depends solely on available metal concentrations in the soil. Here we show that in the facultative metallophyte Arabidopsis halleri, both insect herbivory and mechanical wounding of leaves trigger an increase specifically in leaf Cd accumulation. Moreover, the Cd concentrations accumulated in leaves can serve as an elemental defense against herbivory by larvae of the Brassicaceae specialist small white (Pieris rapae), thus allowing the plant to take advantage of this non-essential trace element and toxin. Metal homeostasis genes are overrepresented in the systemic transcriptional response of roots to the wounding of leaves in A. halleri, supporting that leaf Cd accumulation is preceded by systemic signaling events. A similar, but quantitatively less pronounced transcriptional response was observed in A. thaliana, suggesting that the systemically regulated modulation of metal homeostasis in response to leaf wounding also occurs in non-hyperaccumulator plants. This is the first report of an environmental stimulus influencing metal hyperaccumulation.

Among-population variation in tolerance to larval herbivory by Anthocharis cardamines in the polyploid herb Cardamine pratensis.

Plants have two principal defense mechanisms to decrease fitness losses to herbivory: tolerance, the ability to compensate fitness after damage, and resistance, the ability to avoid damage. Variation in intensity of herbivory among populations should result in variation in plant defense levels if tolerance and resistance are associated with costs. Yet little is known about how levels of tolerance are related to resistance and attack intensity in the field, and about the costs of tolerance. In this study, we used information about tolerance and resistance against larval herbivory by the butterfly Anthocharis cardamines under controlled conditions together with information about damage in the field for a large set of populations of the perennial plant Cardamine pratensis. Plant tolerance was estimated in a common garden experiment where plants were subjected to a combination of larval herbivory and clipping. We found no evidence of that the proportion of damage that was caused by larval feeding vs. clipping influenced plant responses. Damage treatments had a negative effect on the three measured fitness components and also resulted in an earlier flowering in the year after the attack. Tolerance was related to attack intensity in the population of origin, i.e. plants from populations with higher attack intensity were more likely to flower in the year following damage. However, we found no evidence of a relationship between tolerance and resistance. These results indicate that herbivory drives the evolution for increased tolerance, and that changes in tolerance are not linked to changes in resistance. We suggest that the simultaneous study of tolerance, attack intensity in the field and resistance constitutes a powerful tool to understand how plant strategies to avoid negative effects of herbivore damage evolve.

Male-derived butterfly anti-aphrodisiac mediates induced indirect plant defense.

Plants can recruit parasitic wasps in response to egg deposition by herbivorous insects-a sophisticated indirect plant defense mechanism. Oviposition by the Large Cabbage White butterfly Pieris brassicae on Brussels sprout plants induces phytochemical changes that arrest the egg parasitoid Trichogramma brassicae. Here, we report the identification of an elicitor of such an oviposition-induced plant response. Eliciting activity was present in accessory gland secretions released by mated female butterflies during egg deposition. In contrast, gland secretions from virgin female butterflies were inactive. In the male ejaculate, P. brassicae females receive the anti-aphrodisiac benzyl cyanide (BC) that reduces the females' attractiveness for subsequent mating. We detected this pheromone in the accessory gland secretion released by mated female butterflies. When applied onto leaves, BC alone induced phytochemical changes that arrested females of the egg parasitoid. Microarray analyses revealed a similarity in induced plant responses that may explain the arrest of T. brassicae to egg-laden and BC-treated plants. Thus, a male-derived compound endangers the offspring of the butterfly by inducing plant defense. Recently, BC was shown to play a role in foraging behavior of T. brassicae, by acting as a cue to facilitate phoretic transport by mated female butterflies to oviposition sites. Our results suggest that the anti-aphrodisiac pheromone incurs fitness costs for the butterfly by both mediating phoretic behavior and inducing plant defense.

Plant defence signalling induced by biotic attacks.

Induced defence responses are elicited when plants are exposed to biotic stresses such as attack by herbivores or pathogens. In nature, plants are often subjected to attack by more than one organism, and defence responses elicited by one organism can thereby be modified by the presence of another. Below-ground attack can influence responses to above-ground attack and vice versa, due to systemic induction of defence metabolism. In some interactions defence is enhanced through prior attack by another organism, whereas in others there are conflicting signals. Recent research has shown how plants integrate these signals to coordinate defence by regulation of key metabolic pathways, although there is still much to be learnt.

Changing green leaf volatile biosynthesis in plants: an approach for improving plant resistance against both herbivores and pathogens.

Green leaf volatiles (GLVs) are commonly emitted by green plants, and their production is drastically enhanced when they are under biotic stress. To clarify the ecological function of naturally emitted GLVs, we studied the response of Arabidopsis, whose GLV biosynthesis had been modified, when subjected to herbivory or a pathogenic infection. There was a significant increase in GLV production after herbivory by cabbage white butterfly larvae and pathogen (gray mold) infection in hydroperoxide lyase (HPL) sense Arabidopsis compared with WT controls. The HPL sense modification resulted in the plant being more attractive to the parasitic wasp Cotesia glomerata, leading to higher mortality of the herbivores. The HPL sense modification also resulted in greater inhibition of growth of the fungus. By contrast, HPL antisense Arabidopsis produced fewer GLVs, attracted fewer parasitoids, and was more susceptible to the pathogens than the WT control. These data show that (i) one of the ecological functions of GLV biosynthesis related to resistance against both herbivores and pathogens, and (ii) the genetic modification of GLV biosynthesis could be a unique approach for improving plant resistance against such biotic stresses.

Spatial distribution of Aglais urticae (L.) and its host plant Urtica dioica (L.) in an agricultural landscape: implications for Bt maize risk assessment and post-market monitoring.

Over the past decades, genes of Bacillus thuringiensis var. kurstaki (Berliner) (Bt) coding for protein toxins have been engineered into maize for protection against the European Corn Borer (Ostrinia nubilalis (Hbn.)). However, these transgenic plants may have an impact on non-target organisms. In particular, a potential hazard was identified for non-target lepidopteran larvae, if they consume Bt maize pollen on their host plants. Risk can be defined as a function of the effect of an event (hazard) and the likelihood of this event occurring. Although data on toxicity (hazard) are available from many lab and field studies, knowledge about the environmental exposure of European lepidopteran larvae is incomplete at the population level. Therefore we studied the distribution of small tortoiseshell caterpillars (Aglais urticae (L.)) and its host plant in an agricultural landscape in Germany, to estimate the potential population exposure to maize pollen. The results showed that larvae of the small tortoiseshell developed primarily on freshly sprouted nettle stands (Urtica dioica (L.)) in field margins, rather than adjacent to hedges and groves. However, the main distribution was at margins of cereal (non-maize) fields, where 70% of all larvae were found. This may be due the fact that cereals covered 54% of the survey area, while maize only covered 6.1%. On the other hand, maize fields seem so show higher food plant densities than cereal crops. The results must be interpreted carefully, as the data basis of the present study is very small, and the situation can vary between years due to crop rotation or other changes in agricultural practices. Therefore it is still questionable whether the small tortoiseshell is significantly exposed to maize pollen. For a conclusive risk assessment, more replications and surveys of larger areas in different intensively managed agricultural landscapes over several years are needed.

Food-plant niche selection rather than the presence of ant nests explains oviposition patterns in the myrmecophilous butterfly genus Maculinea.

It has been suggested that the socially parasitic butterfly Maculinea alcon detects ant odours before ovipositing on initial larval food plants near colonies of its obligate ant host Myrmica ruginodis. It has also been suggested that overcrowding on food plants near M. ruginodis is avoided by an ability to detect high egg loads, resulting in a switch to selecting plants near less suitable ant species. If confirmed, this hypothesis (H1) would have serious implications for the application of current population models aimed at the conservation of endangered Maculinea species, which are based on the null hypothesis (H0) that females randomly select food plants whose flower buds are at a precise phenological stage, making oviposition independent of ants. If H1 were wrong, practical management based upon its assumptions could lead to the extinction of protected populations. We present data for the five European species of Maculinea which show that (i) each oviposits on a phenologically restricted flower-bud stage, which accounts for the apparent host-ant-mediated niche separation in sympatric populations of Maculinea nausithous and Maculinea teleius, (ii) there is no temporal shift in oviposition by Maculinea arion in relation to host ant distribution or egg density, and (iii) oviposition patterns in 13 populations of M. alcon's closest relative, Macaulinea rebeli, conform to H0 not H1 predictions. It is concluded that conservation measures should continue to be based on H0.

Enfermedades cutáneas producidas por algunos artrópodos en Chile / Cutaneous diseases caused by some arthropods in Chile

Existen muchos artrópodos que afectan al hombre y a animales. Algunos artrópodos sólo producen manifestaciones cutáneas o sistémicas, otros son vectores de diversas enfermedades. Las picaduras y mordeduras de artrópodos son un motivo de consulta muy frecuente en la práctica dermatológica diaria, la mayoría de diagnóstico y tratamiento fácil, sin complicaciones. A veces, sin embargo, las manifestaciones puden ser tan greves que producen la muerte. En ocaciones, por ejemplo, en pacientes que han viajado al extranjero, el diagnóstico de las lesiones puede ser difícil, y es necesario profundizar en los diagnósticos diferenciales. En este artículo revisamos las patologías cutáneas más frecuentes producidas por distintos artrópodos de las clases Insecta y Aracnida, tales como abejas, pulgas, moscas, chinches, vinchucas, arañas y escorpiones. Se describen con detalle las distintas manifestaciones cutáneas y sistémicas y se entregan algunos elementos teóricos en el tratamiento de éstas

[Ocular lesions produced by caterpillars]. / Leziuni oculare produse de omizi.

The caterpillars' tissues contain substances for the stein, mucous membranes and eyes. The paper presents 2 clinical investigations of ocular lesions produced by caterpillars. The first was done on a 7-year-old child who has got toxic keratoconjunctivitis and erythematosus and vesicular type pruriginous cutaneous eruption after crashing of a caterpillar, because of its specific toxin. The phenomena diminish after large ocular washings, and the cutaneous toxic phenomena retrocead after antipruriginous lotions and general administration of antihistaminics. The later investigation was done on a 17-year-old patient with toxic iridocyclitis and fibrinous dense exudate due to caterpillar's hair. The anatomopathological exam of the iris showed lymphoplasmocitary infiltrate with many eosinophils. The ocular inflammation was due to caterpillar's hair presence in the anterior chamber and also to the toxin freed. The hair elimination from the anterior chamber determined the cure of the disease.