Effects of Rewarding and Unrewarding Experiences on the Response to Host-induced Plant Odors of the Generalist Parasitoid <Emphasis Type="BoldItalic">Cotesia marginiventris</Emphasis> (Hymenoptera: Braconidae)

Associative learning is known to modify foraging behavior in numerous parasitic wasps. This is in agreement with optimal foraging theory, which predicts that the wasps will adapt their responses to specific cues in accordance with the rewards they receive while perceiving these cues. Indeed, the generalist parasitoid Cotesia marginiventris shows increased attraction to a specific plant odor after perceiving this odor during contact with hosts. This positive associative learning is common among many parasitoids, but little is known about the effects of unrewarding host searching events on the attractiveness of odors. To study this, preferences of female C. marginiventris for herbivore-induced odors of three plant species were tested in a six-arm olfactometer after the wasps perceived one of these odors either i) without contacting any caterpillars, ii) while contacting the host caterpillar Spodoptera littoralis, or iii) while contacting the non-host caterpillar Pieris rapae. The results confirm the effects of positive associative learning, but showed no changes in innate responses to the host-induced odors after “negative” experiences. Hence, a positive association is made during an encounter with hosts, but unsuccessful host-foraging experiences do not necessarily lead to avoidance learning in this generalist parasitoid.     

Differential leaf traits of a neotropical tree Cariniana legalis (Mart.) Kuntze (Lecythidaceae): comparing saplings and emergent trees

Cariniana legalis is an emergent tree that reaches the upper canopy in Brazilian Semideciduous Forest. Spatial contrasts in microclimatic conditions between the upper canopy and understorey in a forest may affect morpho-physiological leaf traits. In order to test the hypothesis that the upper canopy is more stressful to leaves than a gap environment we compared emergent trees of C. legalis, 28–29 m in height to gap saplings, 6–9 m in height, for the following parameters: leaf area, leaf mass area (LMA the dry weight:leaf area ratio), leaf thickness, leaf anatomical parameters, stomata conductance, and chlorophyll a fluorescence. Leaves from emergent trees had smaller leaf areas but greater LMA compared to saplings. Leaf thickness, palisade layer thickness, and stomatal density were higher for emergent trees than for saplings. The opposite pattern was observed for spongy layer thickness and spongy/palisade ratio. Stomatal conductance was also higher for emergent tree leaves than for sapling leaves, but the magnitude of depression on stomatal conductance near midday was more pronounced in emergent trees. The potential quantum yield of photosystem II, as determined by the F _v/F _m ratio was lower for leaves from saplings. The lower values of stomatal conductance, indicating restriction in CO₂ diffusion into the mesophyll can be related to higher photoinhibition observed in the saplings. Leaves from emergent trees and saplings exhibited similar values for apparent electron transport rates and non-photochemical quenching. Our results suggest that changes in leaf traits could be associated to dry conditions at the upper canopy as well as to the ontogenetic transition between sapling/emergent tree life stages.     

Indicators for biodiversity and ecosystem services: towards an improved framework for ecosystems assessment

Ecosystem assessment and monitoring requires the development and application of suitable indicators, i.e. they need to be (i) reliable and capable of simplifying complex relationships, (ii) quantifiable and transparent in order to enable an easy communication, and (iii) fit for the purpose of indication. These requirements are scarcely fulfilled in current ecosystem assessment and monitoring efforts to address the requirements of international biodiversity conventions. Here we present and test a set of seven criteria towards an improved framework for ecosystems indication with particular emphasis on the indication of biodiversity and ecosystem services: purpose of indication, indicator type according to the EEA’s Driver-Pressure-State-Impact-Response scheme, direct/indirect linkages to biodiversity and ecosystem services, spatial scale and scalability across scales, applicability of benchmarks/reference values, availability of data and protocols, and applicability of remote sensing. The criteria are tested using 24 indicators of ecosystem assessment and monitoring at the global, continental and regional scale. Based on the general trends revealed by our evaluation, we present recommendations to streamline and improve ecosystem indication with respect to international biodiversity conventions. The implementation of our recommendations does require concerted international effort, comparable, for instance, to the implementation of the Water Framework Directive in Europe.     

Thigmomorphogenesis in Solanum lycopersicum: Morphological and biochemical responses in stem after mechanical stimulation

The activation of the phenylpropanoid pathway in plants by environmental stimuli is one of the most universal biochemical stress responses known. In tomato plant, rubbing applied to a young internode inhibit elongation of the rubbed internode and his neighboring one. These morphological changes were correlated with an increase in lignification enzyme activities, phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidases (POD), 24 hours after rubbing of the forth internode. Furthermore, a decrease in indole-3-acetic acid (IAA) content was detected in the rubbed internode and the upper one. Taken together, our results suggest that decrease in rubbed internode length is a consequence of IAA oxidation, increases in enzyme activities (PAL, CAD and POD), and cell wall rigidification associated with induction of lignification process.Key words: Mechanical stimulation, PAL, CAD, POD, IAAIn their environment, plants are constantly submitted to several stimuli such as wind, rain and wounding. The growth response of plants to such stimuli was termed thigmomorphogenesis and was observed in a wide range of plants.^1–3 The most common thigmomorphogenetic response is a retardation of tissue elongation accompanied by an increase in thickness.⁴ The plant response to mechanical perturbation is mainly restricted to the young developing internode, since no influence can be detected when the internode has reached its final length.^5,6 These plant growth modifications, which characterize thigmomorphogenesis, are related to biochemical events associated with lignification process⁷ and ethylene production.^8,9In tomato plant the length of internodes 4 (N4) and 5 (N5) was measured 14 days after rubbing of the fourth internode. Results reported in Figure 1 show that rubbing led to a significant reduction of elongation of the stressed internode (N4) (decrease of N4 length from 4.3 cm in the control plant to 2.9 in the rubbed one). This effect was not limited to the rubbed area but affected also the elongation of the neighboring internodes (N5) that were shorter in rubbed plants than in control ones.Open in a separate windowFigure 1Internode lengths of control and rubbed plants measured 14 day after mechanical stress applied to the fourth internode. Standard errors are indicated by vertical bars.Results reported in Figure 2 show an increase in PAL activity in both internodes N4 and N5, 24 hours after mechanical stress application as compared with corresponding controls. CAD activity was also investigated in N4 and N5, 24 h after rubbing of the fourth internode. Results presented in Figure 3 show that mechanical stress application induces a strong increase of CAD activity in the rubbed internode N4 (5.3 nkatal μg-1 protein) with an approximately two-fold increase when compared to control tomato internodes (2.3 nkatal μg-1 protein). Further, CAD activity in N5 was also increased in the rubbed internode (5.538 nkatal μg-1 protein) as compared with the control one (3.256 nkatal μg-1 protein).Open in a separate windowFigure 2PAL activity of internode 4, and 5 in control and rubbed plants 24 h after rubbing of the fourth internode. Standard errors are indicated by vertical bars.Open in a separate windowFigure 3CAD activity of internode 4, and 5 in control and rubbed plants 24 h after rubbing of the fourth internode. Standard errors are indicated by vertical bars.Syringaldazine (S-POD) and gaïacol (G-POD) peroxidase activities were measured in tomato N4 and N5. Results reported in Figure 4 show an increase in soluble peroxidase activity with both substrates in the rubbed internode N4 as compared with control plant. Enhancement in peroxidase activities in N4 was more pronounced with gaïacol (80.7 U) as an electron donor than syringaldazine (33.8 U). Similar results were observed in internode 5 as compared with control one (Fig. 4).Open in a separate windowFigure 4(A) Syringaldazine-POD (Syr-POD) activity of internode 4 and 5 in control and rubbed plants 24 h after rubbing of the fourth internode. Standard errors are indicated by vertical bars. (B) Gaiacol-POD (G-POD) activity of internode 4 and 5 in control and rubbed plants 24 h after rubbing of the fourth internode. Standard errors are indicated by vertical bars.IAA was quantified in control and rubbed plant internodes 24 h after rubbing of the fourth internode. Results reported in figure 5 show that in control sample and as expected, the content of IAA was found to be higher in the younger internode (N5) as compared to the older one (N4). Rubbing led to a significant decrease in IAA levels in N4 (5.06 nmol g⁻¹ MF⁻¹) as compared with corresponding controls (7.27 nmol g⁻¹ MF⁻¹). Similar results were observed in internode 5, where IAA content was reduced from 16.52 nmol g⁻¹ MF⁻¹ in control internode to 12.35 nmol g⁻¹ MF⁻¹ in the rubbed internode (Fig. 5).Open in a separate windowFigure 5IAA Level of internode 4 and 5 in control and rubbed plants 24 h after rubbing of the fourth internode. Standard errors are indicated by vertical bars.The results reported here establish an evident correlation between growth limitation of the rubbed internode and their degree of lignification, the increase in lignification enzymes activities and auxin degradation after mechanical stress application.Auxin seems to be involved in thigmomorphogenesis.¹⁰ It was proposed that MIS (Mechanically-induced stress) has opposite effects on auxin levels in the two species studied to date, Phaseolus vulgaris¹⁰ and Bryonia dioica.^11,12 Auxin level as measured by bioassay, increased in Phaseolus vulgaris following rubbing of the stem.¹⁰ It was proposed that a build up of auxin may result from the reduced polar transport of IAA at the rubbed internode, causing a build up of IAA in the stem tissue. Exogenous IAA did not reverse the MIS inhibition of growth in Phaseolus vulgaris and high levels of IAA retarded growth in non-stressed plants.¹⁰ Thus, retardation of extension growth in Phaseolus vulgaris may have been caused by high levels of endogenous auxin and the increase in stem diameter by increased ethylene production.⁴ However, ethylene increases radial growth only if auxin is present.¹³Boyer¹¹ reported a decrease in auxinlike activity in Bryonia dioica following MIS and this was confirmed in the same species by Hofinger et al.¹² who reported a decrease in IAA using gas chromatography-mass spectrometry. Auxin catabolism was accompanied with changes in both soluble and ionically bound cell wall basic peroxidases¹⁴ and the appearance of an additional peroxidase. This can suggest that in Bryonia, auxin catabolism is hastened by mechanical stimulated peroxidase. In addition, Boyer et al.¹⁵ reported that lithium pre-treatment prevents both thigmomorphogenesis and appearance of specific cathodic isoperoxidase in Bryonia plants subjected to MIS. This is give further credence to the possibility that the peroxidase-auxin system is involved in Bryonia thigmomorphogenesis. In addition, ethylene increases peroxidase activity which reduces the auxin content in the tissue to a level low enough not to support normal growth. We have evidence that decrease of auxin level contribute to mechanism leading to tomato internode inhibition subjected to mechanical stress.Growth inhibition has been suggested to be the result of tissues lignification.⁶ As the initial enzyme in the monolignol biosynthesis pathway, PAL has a direct influence on lignin accumulation.¹⁶ The characteristics of lignin differ among cell wall tissues and plant organs.¹⁷ It comprises polyphenolic polymers derived from the oxidative polymerization of different monolignols, including p-coumaryl, coniferyl and sinapyl alcohols via a side pathway of phenylalanine metabolism leading to lignin synthesis.¹⁸ The increase in lignin content in the rubbed tomato internode could be a response mechanism to mechanical damage caused by rubbing.³ It is known that plants create a natural barrier that includes lignin and suberin synthesis, components directly linked to support systems.^19,20The increase in lignin content of rubbed tomato internode³ is paralleled by a rise in CAD activity and whilst such direct proportionality between CAD activity and lignin accumulation does not always agree with the results in the literature, it clearly is responding in ways similar to those of the other enzymes in the pathway.²¹Mechanical stress-induced membrane depolarization would generate different species of free radicals and peroxides, which in turn initiate lipid peroxidation.²² The degradation of cell membranes is suggested to bring about rapid changes in ionic flux, especially release of K⁺ which would result in an enhanced endogenous Ca/K ratio and in leakage of solutes, among them electron donors such as ascorbic acid and phenolic substances. The increased intracellular relative calcium level activated secretion of basic peroxidases²³ into the free space where, in association with the electron donors and may be with the circulating IAA, they eliminate the peroxides, and facilitated binding of basic peroxidases to membrane structures allowing a role as 1-aminocyclopropane-1-carboxylic acid (ACC)-oxidases. The resulting IAA and ACC oxidase-mediated changes in ethylene production²⁴ would further induce (this time through the protein synthesis machinery) an increase in activity of phenylalanine ammonia-lyase and peroxidases. The resulting lignification and cell wall rigidification determines the growth response of tomato internode to the mechanical stress.     

Alternative Splicing at a NAGNAG Acceptor Site as a Novel Phenotype Modifier

Approximately 30% of alleles causing genetic disorders generate premature termination codons (PTCs), which are usually associated with severe phenotypes. However, bypassing the deleterious stop codon can lead to a mild disease outcome. Splicing at NAGNAG tandem splice sites has been reported to result in insertion or deletion (indel) of three nucleotides. We identified such a mechanism as the origin of the mild to asymptomatic phenotype observed in cystic fibrosis patients homozygous for the E831X mutation (2623G>T) in the CFTR gene. Analyses performed on nasal epithelial cell mRNA detected three distinct isoforms, a considerably more complex situation than expected for a single nucleotide substitution. Structure-function studies and in silico analyses provided the first experimental evidence of an indel of a stop codon by alternative splicing at a NAGNAG acceptor site. In addition to contributing to proteome plasticity, alternative splicing at a NAGNAG tandem site can thus remove a disease-causing UAG stop codon. This molecular study reveals a naturally occurring mechanism where the effect of either modifier genes or epigenetic factors could be suspected. This finding is of importance for genetic counseling as well as for deciding appropriate therapeutic strategies.     

Plasma BDNF concentration,Val66Met genetic variant and depression‐related personality traits

Brain‐derived neurotrophic factor (BDNF) regulates synaptic plasticity and neurogenesis, and BDNF plasma and serum levels have been associated with depression, Alzheimer's disease, and other psychiatric and neurodegenerative disorders. In a relatively large community sample, drawn from the Baltimore Longitudinal Study of Aging (BLSA), we examine whether BDNF plasma concentration is associated with the Val66Met functional polymorphism of the BDNF gene (n = 335) and with depression‐related personality traits assessed with the NEO‐PI‐R (n = 391). Plasma concentration of BDNF was not associated with the Val66Met variant in either men or women. However, in men, but not in women, BDNF plasma level was associated with personality traits linked to depression. Contrary to the notion that low BDNF is associated with negative outcomes, we found lower plasma levels in men who score lower on depression and vulnerability to stress (two facets of Neuroticism) and higher on Conscientiousness and Extraversion. These findings challenge the prevailing hypothesis that lower peripheral levels of BDNF are a marker of depression.     

Development,characterization, validation,and mapping of SSRs derived from <Emphasis Type="Italic">Theobroma cacao</Emphasis> L.<Emphasis Type="Italic">–Moniliophthora perniciosa</Emphasis> interaction ESTs

In this study, we report results of the detection and analysis of SSR markers derived of cacao–Moniliophthora perniciosa expressed sequence tags (ESTs) in relation to cacao resistance to witches’ broom disease (WBD), and we compare the polymorphism of those ESTs (EST-simple sequence repeat (SSR)) with classical neutral SSR markers. A total of 3,487 ESTs was used in this investigation. SSRs were identified in 430 sequences: 277 from the resistant genotype TSH 1188 and 153 from the susceptible one Catongo, totalizing 505 EST-SSRs with three types of motifs: dinucleotides (72.1%), trinucleotides (27.3%), and tetranucleotides (0.6%). EST-SSRs were classified into 16 main categories; most of the EST-SSRs belonged to “Unknown function” and “No homology” categories (45.82%). A high frequency of SSRs was found in the 5’UTR and in the ORF (about 27%) and a low frequency was observed in the 3’UTR (about 8%). Forty-nine EST-SSR primers were designed and evaluated in 21 cacao accessions, 12 revealed polymorphism, having 47 alleles in total, with an average of 3.92 alleles per locus. On the other hand, the 11 genomic SSR markers revealed a total of 47 alleles, with an average of 5.22 alleles per locus. The association of EST-SSR with the genomic SSR enhanced the analysis of genetic distance among the genotypes. Among the 12 polymorphic EST-SSR markers, two were mapped on the F₂ Sca 6 × ICS 1 population reference for WBD resistance.     

Diet and seed dispersal by five marsupials (Didelphimorphia: Didelphidae) in a Brazilian cerrado reserve

The food habits and seed dispersal promoted by five didelphid marsupials, were investigated through fecal analysis in a cerrado reserve located in the central part of the Espinhaço mountain range in Minas Gerais state, southeastern Brazil. The studied species presented a remarkable constancy in their diets and just for C. philander a seasonal change in diet seems to be present with a high consumption of fruits during the wetter season. Arthropods such as hymenopterans, coleopterans and homopterans were the main food resource detected but seeds belonging to pioneer plants were found with high frequencies in samples of all didelphids. Fruits of pioneer plants belonging to the families Melastomataceae (Clidemia urceolata and Miconia holocericea) and Rubiaceae (Psychotria barbiflora and P. capitata) present high germination rates and were among the mostly consumed. In spite of the differences observed in food preferences, all of the didelphids studied must be considered effective seed dispersers of pioneer plants.     

Parthenogenetic development of domestic cat oocytes treated with ionomycin, cycloheximide, roscovitine and strontium

The objective was to evaluate the parthenogenetic activation of domestic cat oocytes. Cumulus-oocyte complexes matured for 36 h were subjected to three protocols of parthenogenetic activation: Group 1 - ionomycin + cycloheximide; Group 2 - ionomycin + roscovitine; and Group 3 - ionomycin + strontium. As a control, a fourth group of oocytes were cultured in the absence of any activation agent. In all groups, embryos were cultured in SOFaa for 72 h after activation and evaluated for activation rate, cleavage, and embryonic development using Hoechst33342. There were no significant differences among the three treated groups for rates of activated oocytes (70.1 ± 4.3, 75.5 ± 4.7, and 61.9 ± 7.2%, for Treatments 1, 2, and 3 respectively; mean ± SEM), or cleavage (48.1 ± 5.9, 47.4 ± 3.8, and 33.3 ± 6.8%). However, activation and cleavage rates were higher (P < 0.05) than those in the control group (35.5 ± 6.4 and 11.8 ± 4.0%). There were no significant differences among treatment groups for proportion of embryos with 2-10 cells, 10-16 cells, and morulas. In the Control group, the embryo production rate was lower (P < 0.05), although the activation rate was high. The authors concluded that all three treatments effectively induced parthenogenetic activation of domestic cat oocytes. However, to optimize the use of strontium and roscovitine, a dose response and the effect of the presence of Ca⁺⁺ in the medium requires further study.     

Synthesis, characterization, solid-state photo-luminescence and anti-tumor activity of zinc(II) 4′-phenyl-terpyridine compounds

Reactions between 4′-phenyl-terpyridine (L) and several Zn(II) salts (sulfate, nitrate, chloride or acetate) led to the formation of the complexes [Zn₂(μ-O₂SO₂)₂L₂(CH₃OH)₂] (1), [Zn(NO₃)L(H₂O)]NO₃ (2), [Zn(Cl)₂L] (3) and [Zn(CH₃COO)₂L] (4) which were characterized by IR, ¹H NMR and fluorescence spectroscopies, elemental analysis and single crystal X-ray diffraction. In the dinuclear molecule of 1 the Zn atom is hexacoordinated, with a N₃O₃ coordination environment and forms an octagonal ZnOSOZnOSO metallacycle. In the remaining structures, the metal atom is envisaged as possessing highly distorted N₃X₂ (X = O or Cl) square pyramid coordination geometries. The structure of 3 presents two different packing patterns which lead to distinct π-π stackings. In both structures 2 and 4, strong intermolecular hydrogen bonds were identified. The complexes exhibit promising in vitro tumor-inhibiting activities, which are higher than that of cisplatin, against the following human tumor cell lines: promyelocyticfina leukaemia (HL-60), hepatocellular carcinoma (Bel-7402), gastric carcinoma (BGC-823) and nasopharyngeal carcinoma (KB).