Adaptive changes in photosynthetic performance and secondary metabolites during white dead nettle micropropagation

The white dead nettle, Lamium album L., is an herb that has been successfully cultivated under in vitro conditions. The L. album micropropagation system offers a combination of factors (light intensity, temperature, carbon dioxide (CO₂) level, humidity) that are limiting for plant growth and bioactive capacity. To get a better understanding of the mechanism of plant acclimation towards environmental changes, we performed a comparative investigation on primary and secondary metabolism in fully expanded L. album leaves during the consecutive growth in in situ, in vitro, and ex vitro conditions. Although the genetic identity was not affected, structural and physiological deviations were observed, and the level of bioactive compounds was modified. During in vitro cultivation, the L. album leaves became thinner with unaffected overall leaf organization, but with a reduced number of palisade mesophyll layers. Structural deviation of the thylakoid membrane system was detected. In addition, the photosystem 2 (PS2) electron transport was retarded, and the plants were more vulnerable to light damage as indicated by the decreased photoprotection ability estimated by fluorescence parameters. The related CO₂ assimilation and transpiration rates were subsequently reduced, as were the content of essential oils and phenolics. Transfer of the plants ex vitro did not increase the number of palisade numbers, but the chloroplast structure and PS2 functionality were recovered. Strikingly, the rates of CO₂ assimilation and transpiration were increased compared to in situ control plants. While the phenolics content reached normal levels during ex vitro growth, the essential oils remained low. Overall, our study broadens the understanding about the nature of plant responses towards environmental conditions.     

Butterfly Host Plant Choice in the Face of Possible Confusion

We tested predictions from the theory that ovipositing females of phytophagous insects are limited by their neural capacity for information processing. Previous studies have found that relatively specialized insects make faster and/or more accurate identifications of host plants compared to generalists. The study species was the polyphagous comma butterfly, Polygonia c-album (Nymphalidae). We compared females originating from two populations (Sweden and England) which differ in degree of specialization on the preferred host Urtica dioica (Urticaceae). Females were given a choice between this plant and a very similar nonhost, white dead nettle, Laminum album (Lamiacease), or a choice between a relatively poor host, Betuala pubescens, and the nonhost Betula pendula (Betulaceae). Oviposition rate was lower in cages with Betula compared to cages with Urtica, demonstrating that P. c-album females will withhold eggs when preferred hosts are not available. As predicted, females originating from the Swedish generalist population oviposited more often on the nonhost Lamium. However, females of both populations discriminated very strongly against oviposition on B. pendula. We found that newly hatched larvae have some ability to move from herbaceous nonhost to hosts. Although alternative interpretations are possible, the results give further support to the hypothesis that there are trade-offs between diet breadth and the ability to discriminate among plants.     

Novel aminoalkaloids from European mistletoe (Viscum album L.)

The European white-berry mistletoe (Viscum album L.) has remained an important medicinal plant for millennia. Preparations of the plant have found application in the treatment of cancer and the anticancer activity of mistletoe extracts has been ascribed to the presence of lectins, viscotoxins and alkaloids. However, the alkaloids of this species have hitherto remained unidentified because of their claimed extreme lability. Here we report on the isolation and characterisation of the novel aminoalkaloids 4,5,4′-trihydroxy-3,3′-iminodibenzoic acid (1) and 4,5,4′,5′-tetrahydroxy-3,3′-iminodibenzoic acid (2) from V. album L. The compounds define a novel group of aminoalkaloids and are the first novel alkaloids ever identified in any mistletoe species. The structures were established using a combination of several 2D NMR spectroscopic techniques and high resolution mass spectrometry.     

Host feeding experience affects host plant odour preference of the polyphagous leafminer Liriomyza bryoniae

Herbivorous insects use highly specific volatiles or blends of volatiles characteristic to particular plant species to locate their host plants. Thus, data on olfactory preferences can be valuable in developing integrated pest management tools that deal with manipulation of pest insect behaviour. We examined host plant odour preferences of the tomato leafminer, Liriomyza bryoniae (Kaltenbach) (Diptera: Agromyzidae), which is an economically important agricultural pest widespread throughout Europe. The odour preferences of leafminers were tested in dependence of feeding experiences. We ranked host plant odours by their appeal to L. bryoniae based on two‐choice tests using a Y‐tube olfactometer with five host plants: tomato, Solanum lycopersicum Mill.; bittersweet, Solanum dulcamara L.; downy ground‐cherry, Physalis pubescens L. (all Solanaceae); white goosefoot, Chenopodium album L. (Chenopodiaceae); and dead nettle, Lamium album L. (Lamiaceae). The results imply that ranking of host plant odours by their attractiveness to L. bryoniae is complicated due to the influence of larval and adult feeding experiences. Without any feeding experience as an adult, L. bryoniae males showed a preference for the airflow with host plant odour vs. pure air, whereas females did not display a preference. Further tests revealed that adult feeding experience can alter the odour choice of L. bryoniae females. After feeding experience, females showed a preference for host plant odour vs. pure air. Feeding experience in the larval stage influenced the choice by adults of both sexes: for males as well as females reared on bittersweet the odour of that plant was the most attractive. Thus, host feeding experience both in larval and/or adult stage of polyphagous tomato leafminer L. bryoniae influences host plant odour preference by adults.     

Parengyodontium album,a frequently reported fungal species in the cultural heritage environment

Fungi are one of the main agents responsible for the biodeterioration of cultural heritage through physical and chemical processes. The frequent isolation of certain fungal species from deteriorated materials indicates that these species appear to have a particular affinity for environmental conditions occurring in cultural heritage. It is important to identify the conditions that favour the development of such species in order to understand how to preserve monuments and collections. Among these fungal species, the involvement of Parengyodontium album (Limber) Tsang et al. seems to have been underestimated until now. This species is abundant in many environments and its taxonomic position has changed quite frequently, which may have concealed the effect of this fungus on cultural heritage sites. This review seeks to compile the involvement of P. album in cultural heritage biodeterioration phenomena under all the names that it has been attributed in order to effectively determine its occurrence. This paper also aims to determine whether P. album is marginal or dominant when detected on materials. Finally, the conditions that favour the development of P. album on cultural heritage objects and sites are discussed.     

Activation of non-photochemical quenching in thylakoids and leaves

The mechanism of rapidly-relaxing non-photochemical quenching in two plant species,Chenopodium album L. andDigitalis purpurea L., that differ considerably in their capacity for such quenching has been investigated (Johnson G.N. et al. 1993, Plant Cell Environ.16, 673–679). Illumination of leaves of both species in the presence of 2% O₂ balance N₂ led to the formation of zeaxanthin. When thylakoids were isolated from leaves of each species that had been so treated it was found that inD. purpurea non-photochemical quenching was “activated” relative to the control; a higher level of quenching was found for a given trans-thylakoid pH gradient. No such activation of non-photochemical quenching was observed inC. album. Similar conclusions were drawn when comparing quenching in intact leaves. It is concluded that light activation of quenching is a process that cannot readily be induced inC. album. Measurement of the sensitivity of non-photochemical quenching in leaves ofC. album andD. purpurea to dithiothreitol (DTT; a reagent that inhibits formation of zeaxanthin) showed differences between the two species. In both cases, feeding leaves with DTT inhibited the light-induced formation of zeaxanthin. InC. album this was accompanied by complete inhibition of reversible non-photochemical quenching, whereas inD. purpurea this inhibition was only partial. Data are discussed in relation to studies on the mechanism of quenching and the role of zeaxanthin in this process.     

The Use of Olfactory and Visual Cues in Host Choice by the Capsid Bugs Lygus rugulipennis Poppius and Liocoris tripustulatus Fabricius

Lygus rugulipennis Poppius and Liocoris tripustulatus Fabricius (Heteroptera: Miridae) are pests of glasshouse cucumber and sweet pepper crops respectively. L. rugulipennis has a wide range of foodplants, but L. tripustulatus is specialised with very few food plants. We report behavioural assessments to investigate whether either species exhibits a preference for salad over wild hosts, and whether the role of olfaction and vision in response to cues from host plants can be distinguished. Olfactory responses to leaves were tested in choice chambers. L. rugulipennis was presented nettle (wild host) and a salad leaf of cucumber or sweet pepper, where the salad leaves had higher nitrogen content. L. tripustulatus was tested with nettle and sweet pepper of two different nitrogen contents. Female L. rugulipennis spent more time on the cucumber salad host, and chose it first most often, but males showed no preference. Neither sex discriminated between sweet pepper or nettle leaves, but males made more first contacts with sweet pepper. Neither sex of L. tripustulatus discriminated between sweet pepper and nettle leaves when the sweet pepper had higher nitrogen. When the plant species contained equivalent nitrogen both sexes spent more time on nettle. There was no difference in first choice made by either sex. When visual stimuli were available, and leaves had equivalent nitrogen, L. rugulipennis showed no preference and L. tripustulatus preferred nettle leaves. We conclude that the generalist L. rugulipennis has the ability to use remote olfactory cues for host choice whereas the specialist L. tripustulatus relies mainly on contact chemosensory and gustatory cues.     

The role of female search behaviour in determining host plant range in plant feeding insects: a test of the information processing hypothesis

Recent theoretical studies have suggested that host range in herbivorous insects may be more restricted by constraints on information processing on the ovipositing females than by trade-offs in larval feeding efficiency. We have investigated if females from polyphagous species have to pay for their ability to localize and evaluate plants from different species with a lower ability to discriminate between conspecific host plants with differences in quality. Females of the monophagous butterflies Polygonia satyrus, Vanessa indica and Inachis io and the polyphagous P. c-album and Cynthia cardui (all in Lepidoptera, Nymphalidae) were given a simultaneous choice of stinging nettles (Urtica dioica) of different quality. In addition, the same choice trial was given to females from two populations of P. c-album with different degrees of specificity. As predicted from the information processing hypothesis, all specialists discriminated significantly against the bad quality nettle, whereas the generalists laid an equal amount of eggs on both types of nettle. There were no corresponding differences between specialist and generalist larvae in their ability to utilize poor quality leaves. Our study therefore suggests that female host-searching behaviour plays an important role in determining host plant range.     

Arbuscular mycorrhizal fungi as (agro)ecosystem engineers

Symbiotic interactions have been shown to facilitate shifts in the structure and function of host plant communities. For example, parasitic plants can induce changes in plant diversity through the suppression of competitive community dominants. Arbuscular mycorrhizal (AM) fungi have also be shown to induce shifts in host communities by increasing host plant nutrient uptake and growth while suppressing non-mycorrhizal species. AM fungi can therefore function as ecosystem engineers facilitating shifts in host plant communities though the presumed physiological suppression of non-contributing or non-mycorrhizal plant species. This dichotomy in plant response to AM fungi has been suggested as a tool to suppress weed species (many of which are non-mycorrhizal) in agro-ecosystems where mycorrhizal crop species are cultivated. Rinaudo et al. (2010), this issue, have demonstrated that AM fungi can suppress pernicious non-mycorrhizal weed species including Chenopodium album (fat hen) while benefiting the crop plant Helianthus annuus (sunflower). These findings now suggest a future for harnessing AM fungi as agro-ecosystem engineers representing potential alternatives to costly and environmentally damaging herbicides.     

Seed treatment with aqueous extract of Viscum album induces resistance to pearl millet downy mildew pathogen

Abstract

Downy mildew (Sclerospora graminicola [Sacc.] Schroet.) is a serious agricultural problem for pearl millet (Pennisetum glaucum [L.] R. Br.) grain production under field conditions. Six medicinally important plant species Azadirachta indica, Argemone mexicana, Commiphora caudata, Mentha piperita, Emblica officinalis and Viscum album were evaluated for their efficacy against pearl millet downy mildew. Seeds of pearl millet were treated with different concentrations of aqueous extract of the plants to examine their efficacy in controlling downy mildew. Among the plant extracts tested, V. album treatment was found to be more effective in enhancing seed quality parameters and also in inducing resistance against downy mildew disease. Germination and seedling vigor was improved in seeds treated with V. album extracts over control. Seeds treated with 10% concentration of V. album showed maximum protection against downy mildew disease under greenhouse and field conditions. The downy mildew disease protection varied from 44–70% with different concentrations. Leaf extract of V. album did not inhibit sporulation and zoospore release from sporangia of Sclerospora graminicola, indicating that the disease-controlling effect was attributed to induced resistance. Seed treatment with V. album extract increased pearl millet grain yield considerably. In V. album, treated pearl millet seedlings increased activities of peroxidase, and phenylalanine ammonia-lyase enzyme was detected. FTIR analysis of V. album extracts showed the presence of amides and other aromatic compounds which are antimicrobial compounds involved in plant defense.     

The gene space of European mistletoe (Viscum album)

European mistletoe (Viscum album) is a hemiparasitic flowering plant that is known for its very special life cycle and extraordinary biochemical properties. Particularly, V. album has an unusual mode of cellular respiration that takes place in the absence of mitochondrial complex I. However, insights into the molecular biology of V. album so far are very limited. Since the genome of V. album is extremely large (estimated 600 times larger than the genome of the model plant Arabidopsis thaliana) it has not been sequenced up to now. We here report sequencing of the V. album gene space (defined as the space including and surrounding genic regions, encompassing coding as well as 5′ and 3′ non-coding regions). mRNA fractions were isolated from different V. album organs harvested in summer or winter and were analyzed via single-molecule real-time sequencing. We determined sequences of 39 092 distinct open reading frames encoding 32 064 V. album proteins (designated V. album protein space). Our data give new insights into the metabolism and molecular biology of V. album, including the biosynthesis of lectins and viscotoxins. The benefits of the V. album gene space information are demonstrated by re-evaluating mass spectrometry-based data of the V. album mitochondrial proteome, which previously had been evaluated using the A. thaliana genome sequence. Our re-examination allowed the additional identification of nearly 200 mitochondrial proteins, including four proteins related to complex I, which all have a secondary function not related to respiratory electron transport. The V. album gene space sequences are available at the NCBI.     

Recent change in spatial distribution of the European flat oyster (Ostrea edulis) inferred from field data and empirical models of living oysters and empty shells

Marine coastal areas are increasingly affected by human activities resulting in changes in species and habitat distributions. Understanding these patterns and its causes and consequences is important for conservation and restoration of such changing habitats. One habitat that has been heavily affected by human use are the North Sea oyster beds which once were abundant but have lost large parts of its coastal distribution due to overexploitation. Based on data of living and dead assemblages of Ostrea edulis collected using video transects, we used an ensemble modeling technique to model and predict current and recent distribution of O. edulis along the Swedish west coast where its distribution is, in relative terms, still rather unaffected. We could detect a recent change in the distribution of O. edulis along the coast which to a large extent could be attributed to a change in depth distribution, suggesting that the population of O. edulis have a slightly shallower distribution today than in the past. Although a potential mismatch between living and dead assemblages, caused by a complex combination of biological and environmental conditions, needs to be considered in the interpretations drawn, it may be a way around the lack of suitable background data in management decisions. This provides important information for management and conservation of the native oyster beds. Furthermore, this study illustrates a method for identifying recent changes in species distribution using dead assemblages of bivalves.     

Molecular differentiation of Chenopodium album complex and some related species using ISSR profiles and ITS sequences

The present study was undertaken to understand the genetic differentiation and relationships in various components of C. album complex, C. giganteum and some related species using inter simple sequence repeats (ISSR) profiles and internal transcribed spacer (ITS) sequences. The relationships based on UPGMA dendrograms have shown the heterogenous nature of C. album complex. The 2x taxa while showing close relation among themselves are sharply segregated from 4x and 6x taxa belonging to C. album and C. giganteum. Among the three cytotypes from North Indian plains the 4x shows greater similarity to 6x than to 2x which is corroborated by the karyotypic studies. Furthermore, the 6x C. album and C. giganteum accessions of American and European origin are clearly segregated from those of Indian origin which may show their separate origin. Other related species show relationships according to their taxonomic position. The present study based on ISSR profiles and ITS sequences has therefore been very useful in explaining the relationships between various components of C. album complex and related species. However, more work needs to be done using different CpDNA loci to define correct species boundary of the taxa under C. album complex from Himalayas and North Indian Plains.     

Cover Caption

The photograph shows a fifth instar larva of the comma butterfly (Polygonia c‐album) on a leaf of nettle (Urtica dioica), one of several hosts of this polyphagous species. Neonate comma larvae show a surprising ability to reject unfavourable hosts in search for better suitable ones, a behaviour that may ameliorate a bad oviposition choice (see pages 499–506). Photo by: Niklas Janz©.     

Is hybridization involved in the evolution of the Chenopodium album aggregate? An analysis based on chromosome counts and genome size estimation

For our study of the Chenopodium album aggregate, we selected those species of Euroasiatic origin that represent the diploid–polyploid complex in Central Europe: C. album (6x), C. ficifolium (2x), C. opulifolium (6x), C. striatiforme (4x), C. strictum (4x) and C. suecicum (2x). We especially focused on (a) the origin of polyploid species and (b) the frequency of hybridization between species with different ploidy levels. We did not find any direct evidence of the existence of hybrids between two species with different ploidy levels within the C. album group. The sample/standard ratio of tetraploid and hexaploid species does not equal multiples of that of diploid species, which suggests that (i) tetraploids are not diploid autopolyploids and that (ii) hexaploids have not evolved from diploid species alone. Moreover, we have not found any hybrid plant either in the field or even in the offspring resulting from our experimental crosses. In view of these results, we adhere to the opinion that Chenopodium species do not hybridize freely across ploidy levels. Our analysis of DNA amounts, however, suggests that C. album is an allopolyploid that has arisen by hybridization between a diploid and a tetraploid species the identity of which is unknown.     

Generation of H2O2 by Human Neutrophils and Changes of Cytosolic Ca2+ and pH of Rat Thymocytes in Response to Galactoside-Binding Proteins (Lectins or Immunoglobulins)

In contrast to plant agglutinins, biological activities of animal/human lectins are not well defined yet. Testing a panel of seven mammalian carbohydrate-binding proteins we have found that the dimeric lectin from chicken liver (CL-16) was a stimulator of H₂O₂ release from human neutrophils as well as effector for induction of cytosolic Ca²⁺ and pH increase in rat thymocytes. Activity of this lectin was comparable to potent galactoside-specific plant lectins such as Viscum album L. agglutinin. The activities of the tested plant lectins depended significantly on their nominal carbohydrate specificity as well as on the source. The results indicate that endogenous lectins may be involved in the regulation of neutrophil and lymphocyte functions by elicitation of selective biosignaling reactions.     

Infra-specific genetic and morphological diversity in Linum album (Linaceae)

The genus Linum L. (Lineacea) has over 15 species, subspecies or ecotypes in Iran. These species show extensive geographical distribution and form many local populations throughout the country. Linum album is herbaceous medicinal plant containing important lignans such as podophyllotoxin (PTOX) and 6-methoxy podophyllotoxin (MPTOX), which have antiviral and anticancer properties. Studying the genetic and morphological diversity of different geographical populations produces detailed knowledge about population divergence and identification of the infra-species taxa if at all they are present. Moreover, the populations that differ in their genetic content and structure may also differ in their chemical and medicinal properties. The present study considers morphological and genetic diversity analyses of 20 L. album geographical populations by using nuclear ISSR markers, genome size, and cytogenetic characteristics. These populations differed significantly in many of their quantitative morphological characters and in some of their qualitative features. They also differed significantly in their molecular characteristics and genome size. Details of morphological and molecular variations are reported and discussed.     

Influence of Heterodera glycines on Interspecific and Intraspecific Competition Associated with Glycine max and Chenopodium album

The influence of Heterodera glycines (soybean cyst nematode) on the interspecific and intraspecific competition associated with Glycine max (soybean) and Chenopodium album (common lambsquarters) was studied in 1988 and 1989 in three de Wit replacement series experiments in growth chambers and microplots. Glycine max was grown alone (1 plant/experimental unit), in intraspecific competition (2 plants/experimental unit), in interspecific competition with C. album, and in presence or absence of H. glycines. No significant effects of H. glycines and C. album on G. max growth were observed 14 days after planting. By 42 days after planting, both H. glycines and C. album had a negative (P = 0.05) influence on the growth of G. max. Relative crowding coefficients for G. max were lower and deviated (P = 0.05 and P = 0.001) from 1.0 in the presence of H. glycines, compared to that of C. album and early emerged C. album in the absence of the nematode, respectively. Glycine max, therefore, became less competitive than C. album. There was a trend that the presence of H. glycines decreased the competitiveness of G. max on measures of the aggressivity and relative mixture response. Heterodera glycines decreased the aggressivity of G. max (ca. 150-350%) and increased the relative effects of intraspecific interference on G. max (ca. 10-50%) and interspecific interference (ca. 60-350%) after 42 days of plant growth, compared with plants grown in the absence of H. glycines. No H. glycines x C. album interactions were detected. Observations showed that H. glycines and early emerged C. album inhibited the growth of G. max 5-13%, as measured by plant dry weight.     

Plantlet Regeneration from Encapsulated and Non-encapsulated Desiccated Somatic Embryos of a Forest Tree: Sandalwood (Santalum album L.)

Somatic embryos obtained from embryogenic tissues of sandalwood (Santaium album) were grown on White’s medium containing abscisic acid, (ABA, 1.89, 3.78 or 18.92 μM) and various concentrations of sucrose (87.6 to 350.4 mM) to induce maturation. The embryos were isolated and desiccated for 10, 20 or 30 days: One lot of the desiccated somatic embryos was encapsulated in sodium alginate gel and the other lot was not encapsulated. Both encapsulated and nonencapsulated desiccated embryos showed revival of growth upon rehydration on White’s medium and developed into plants. The desiccation tolerance and regeneration of viable plantlets depended upon the pretreatment given to somatic embryos. Embryogenic tissue subjected to dry state for 30 days showed revival of somatic embryogenesis upon transfer to a fresh nutrient medium. Implications of maturation and desiccation of somatic embryos on its germinability are discussed.