Metabolite specific effects of solar UV-A and UV-B on alder and birch leaf phenolics

We measured the concentrations of ultraviolet (UV)‐absorbing phenolics varying in response to exclusion of either solar UV‐B or both solar UV‐A and UV‐B radiations in leaves of grey alder (Alnus incana) and white birch (Betula pubescens) trees under field conditions. In alder leaves 20 and in birch leaves 13 different phenolic metabolites were identified. The response to UV exclusion varied between and within groups of phenolics in both tree species. The changes in concentration for some metabolites suggest effects of only UV‐A or UV‐B, which band being effective depending on the metabolite. For some other metabolites, the results indicate that UV‐A and UV‐B affect concentrations in the same direction, while for a few compounds there was evidence suggesting opposite effects of UV‐A and UV‐B radiation. Finally, the concentration of some phenolics did not significantly respond to solar UV. We observed only minor effects on the summed concentration of all determined phenolic metabolites in alder and birch leaves, thus indicating that measuring only total phenolics concentration may not reveal the effects of radiation. Here, we show that the appropriate biological spectral weighting functions for plant‐protective responses against solar UV radiation extend in most cases – but not always – into the UV‐A region and more importantly that accumulation of different phenolic metabolites follows different action spectra. This demonstrates under field conditions that some of the implicit assumptions of earlier research simulating ozone depletion and studying the effects of UV radiation on plant secondary metabolites need to be reassessed.     

Molecular phylogeny of the ant tribe Myrmicini (Hymenoptera: Formicidae)

The interrelationships within ant subfamilies remain elusive, despite the recent establishment of the phylogeny of the major ant lineages. The tribe Myrmicini belongs to the subfamily Myrmicinae, and groups morphologically unspecialized genera. Previous research has struggled with defining Myrmicini, leading to considerable taxonomic instability. Earlier molecular phylogenetic studies have suggested the nonmonophyly of Myrmicini, but were based on limited taxon sampling. We investigated the composition of Myrmicini with phylogenetic analyses of an enlarged set of taxa, using DNA sequences of eight gene fragments taken from 37 representatives of six of the seven genera (Eutetramorium, Huberia, Hylomyrma, Manica, Myrmica, and Pogonomyrmex), and eight outgroups. Our results demonstrate the invalidity of Myrmicini as currently defined. We recovered sister‐group relationships between the genera Myrmica and Manica, and between Pogonomyrmex and Hylomyrma. This study illustrates that to understand the phylogeny of over 6000 myrmicine species, comprehensive taxon sampling and DNA sequencing are an absolute requisite. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 482–495.     

Analyses of the secretomes of Erwinia amylovora and selected hrp mutants reveal novel type III secreted proteins and an effect of HrpJ on extracellular harpin levels

Erwinia amylovora is a plant pathogenic enterobacterium that causes fire blight disease of apple, pear and other rosaceous plants. A type III (T3) secretion system, encoded by clustered, chromosomal hrp genes (hypersensitive response and pathogenicity), is essential for infection, but only a few proteins are known that are secreted through this pathway (the T3 'secretome'). We developed an efficient protocol for purification and concentration of extracellular proteins and used it to characterize the T3 secretome of E. amylovora Ea273 by comparing preparations from the wild-type strain with those from mutants defective in hrp secretion, regulation, or in genes encoding putative T3-secreted proteins. Proteins were resolved by gel electrophoresis and identified using mass spectrometry and a draft sequence of the E. amylovora genome. Twelve T3-secreted proteins were identified, including homologues of known effector and helper proteins, and HrpJ, a homologue of YopN of Yersinia pestis . Several previously uncharacterized T3-secreted proteins were designated as Eops for Erwinia outer proteins. Analysis of the secretome of a non-polar hrpJ mutant demonstrated that HrpJ is required for accumulation of wild-type levels of secreted harpins. HrpJ was found to be essential for pathogenesis, and to play a major role in elicitation of the hypersensitive reaction in tobacco.     

The use of unlicensed bone marrow–derived platelet lysate–expanded mesenchymal stromal cells in colitis: a pre-clinical study

Background

Mesenchymal stromal cells (MSCs) are a promising candidate for treatment of inflammatory disorders, but their efficacy in human inflammatory bowel diseases (IBDs) has been inconsistent. Comparing the results from various pre-clinical and clinical IBD studies is also challenging due to a large variation in study designs.

Do elevated atmospheric CO2 and O3 affect food quality and performance of folivorous insects on silver birch?

The individual and combined effects of elevated CO₂ and O₃ on the foliar chemistry of silver birch (Betula pendula Roth) and on the performance of five potential birch‐defoliating insect herbivore species (two geometrid moths, one lymantrid moth and two weevils) were examined. Elevated CO₂ decreased the water concentration in both short‐ and long‐shoot leaves, but the effect of CO₂ on the concentration of nitrogen and individual phenolic compounds was mediated by O₃ treatment, tree genotype and leaf type. Elevated O₃ increased the total carbon concentration only in short‐shoot leaves. Bioassays showed that elevated CO₂ increased the food consumption rate of juvenile Epirrita autumnata and Rheumaptera hastata larvae fed with short‐ and long‐shoot leaves in spring and mid‐summer, respectively, but had no effect on the growth of larvae. The contribution of leaf quality variables to the observed CO₂ effects indicate that insect compensatory consumption may be related to leaf age. Elevated CO₂ increased the food preference of only two tested species: Phyllobius argentatus (CO₂ alone) and R. hastata (CO₂ combined with O₃). The observed stimulus was dependent on tree genotype and the measured leaf quality variables explained only a portion of the stimulus. Elevated O₃ decreased the growth of flush‐feeding young E. autumnata larvae, irrespective of CO₂ concentration, apparently via reductions in general food quality. Therefore, the increasing tropospheric O₃ concentration could pose a health risk for juvenile early‐season birch folivores in future. In conclusion, the effects of elevated O₃ were found to be detrimental to the performance of early‐season insect herbivores in birch whereas elevated CO₂ had only minor effects on insect performance despite changes in food quality related foliar chemistry.     

Effects of ultraviolet (UV) exclusion on the seasonal concentration of photosynthetic and UV-screening pigments in Scots pine needles

The effects of ultraviolet (UV) radiation on the photosynthetic and UV‐screening pigments in needles of Scots pine (Pinus sylvestris L.) saplings were studied in a UV‐exclusion field chamber experiment in northern Finland (67°N) during 2001–2002. The chambers held filters that excluded both UVB and UVA, only UVB, transmitted all UV, or lacked filters. Analyses of control needles (no filter and polyethene filter) showed that the first changes to occur in spring (end of April) was an abrupt increase in the epoxidation state (EPS) of the xanthophyll cycle pigments, likely in relation with the beginning of the photosynthetic activity. The concentration of chlorophyll, lutein, neoxanthin, α‐carotene, β‐carotene, and the size of the xanthophyll cycle pool (violaxanthin+antheraxanthin+zeaxanthin=VAZ) changed only later when needles reached their summer photosynthesis state. Exclusion of UV radiation significantly affected the xanthophyll cycle but not the other photosynthetic pigments analysed. Interestingly, the effects on xanthophylls were dependent on the sampling date. Under UVA/B‐exclusion, the EPS was increased and VAZ pool size was unchanged in April, whereas EPS remained unchanged and the VAZ pool size was reduced in May and June. The existence of two sustained and active antenna modes during winter and summer could be an explanation for the specific UV‐exclusion effect in the different season. A high‐performance liquid chromatography analysis of soluble phenolics showed that the exclusion of UVA/B radiation caused a significant effect on five compounds out of 46 studied, without affecting the concentration of the total soluble phenolics. Under UVA/B‐exclusion, the concentration of three of them (secoisolariciresinol‐glucopyranoside, two unknown) was reduced while the concentration of dicoumaroyl‐astragalin and pinosylvin monomethylether was increased compared with both controls separately. In general, the exclusion of UVA/B caused a stronger effect than the exclusion of UVB on both photosynthetic and UV screening pigments. The effects of UV radiation on xanthophyll cycle pigments were season‐specific and detectable only under stressful spring conditions (freezing temperatures and high irradiance due to snow reflection). The effect on the xanthophyll cycle could be a direct consequence of UV treatments, or an indirect consequence of the changed flavonoid composition, or a combination of both.     

Effects of elevated carbon dioxide and ozone on aphid oviposition preference and birch bud exudate phenolics

The effect of atmospheric change on birch aphid ( Euceraphis betulae Koch) oviposition preference was examined and plant characteristics that are possibly responsible for the observed effects were investigated. It was hypothesized that the increasing concentrations of CO₂ and O₃ affect singly or in combination the oviposition of birch aphids via changes in host plant characteristics. Two genotypes of field-growing silver birch ( Betula pendula Roth) trees (clones 4 and 80), which were exposed to doubled ambient concentration of CO₂ and O₃, singly and in combination, in a 3-year open-top chamber experiment, were used in an aphid oviposition preference test. It was found that elevated CO₂, irrespective of ozone concentration, increased the number of aphid eggs laid on clone 4, but not in clone 80. Several flavonoid aglycones were identified from the exudate coating of birch buds. Although elevated CO₂ and O₃ affected these phenolic compounds in clone 4, the effects did not correlate with the observed changes in aphid oviposition. It is suggested that neither bud length, which was not affected by the treatments, nor surface exudate phenolics mediate birch aphid oviposition preference.     

Red : far-red light ratio and UV-B radiation: their effects on leaf phenolics and growth of silver birch seedlings

The natural variation in quantity and quality of light modifies plant morphology, growth rate and concentration of biochemicals. The aim of two growth‐room experiments was to study the combined effects of red (R) and far‐red (FR) light and ultraviolet‐B (UV‐B) radiation on the concentrations of leaf phenolics and growth and morphology of silver birch (Betula pendula Roth) seedlings. Analysis by high‐performance liquid chromatography showed that the leaves exposed to supplemental FR relative to R contained higher concentrations of total chlorogenic acids and a cinnamic acid derivative than the leaves treated with supplemental R relative to FR. In contrast, concentration of a flavonoid, quercetin 3‐galactoside, was higher in the R + UV‐B leaves than in the FR + UV‐B leaves. The UV‐B induced production of kaempferols, chlorogenic acids and most quercetins were not modified by the R : FR ratio. Growth measurements showed that the leaf petioles and stems of FR seedlings were clearly longer than those of R seedlings, but leaf area was reduced by UV‐B radiation. Results of these experiments show that exposure of silver birch seedlings to supplemental FR compared to R leads to fast elongation growth and accumulation of phenolic acids in the leaves.     

Preference–performance relationship in the gall midge Rabdophaga rosaria: insights from a common‐garden experiment with nine willow clones

1. Oviposition preferences of herbivorous insects are predicted to match offspring performance on different host taxa or on conspecific host genotypes. In gall‐inducing insects, host‐plant properties such as growth rate and gall size, which are determined by plant genotype and growing conditions, may have a significant impact on offspring performance and, hence, should influence oviposition site selection. 2. The present study investigated host preference of the European rosette willow gall midge Rabdophaga rosaria (Loew) in relation to offspring success on seven clones of Salix myrsinifolia Salisb. and two naturally hybridised S. myrsinifolia × phylicifolia L. clones growing in a replicated design in an experimental field under two fertilisation regimes. For each clone, the average growth rate, number of shoot tips, and leaf and gall size were determined, and their effects on midge preference and larval survival were examined. 3. Main shoot height, number of shoot tips, and gall size were significantly affected by clone. The midges clearly preferred certain clones over the others, but preferences were not related to willow growth traits or to gall size. Survival probability was higher in large than in small galls, but females did not prefer large‐leaved clones that produced the biggest rosette galls. Midge oviposition was also uncorrelated with prior rates of leaf‐rust infection and with feeding preferences of voles and folivorous insects. 4. The weak preference–performance relationship of R. rosaria within S. myrsinifolia is probably explained by evolutionary constraints that prevent generalist insects from achieving an ability to discriminate among conspecific hosts of variable quality.