The Effect of Essential Oils from Asteraceae Plants on Behavior and Selected Physiological Parameters of the Bird Cherry-Oat Aphid.

Essential oils (EOs), including those from the Asteraceae plants, have been shown to have promising insecticidal activity against a wide range of insect pests. Understanding the mechanism of action of EOs is one of the studied aspects. The present study aimed to evaluate the effect of essential oils from Achillea millefolium, Santolina chamaecyparissus, Tagetes patula and Tanacetum vulgare on the settling and probing behavior of the bird cherry-oat aphid (Rhopalosiphum padi L.). In addition, the effect of the oils on the activity of such enzymes as trypsin, pepsin and α- and ß-glucosidase involved in the metabolism of proteins and sugars of the insects was examined. The leaf-choice bioassays demonstrated that the studied EOs limited aphid settling for at least 24 h after the treatment. The application of EOs also inferred with aphid probing behavior by reducing the total probing time and total duration of phloem sap ingestion. Aphids spent more time in the search phase due to an increase in the number and total duration of pathway phases. Moreover, the activity of the studied proteases and glucosidases significantly decreased in R. padi females exposed to the EOs. The enzyme inhibition varied depending on the applied oil and exposure time. Generally, the EOs with stronger deterrent activity also showed higher inhibitory effects. The results suggest that the tested EOs disrupt key digestive processes in R. padi which may be an important factor determining their aphicidal activity.

The Effect of Santolina chamaecyparissus and Tagetes patula Essential Oils on Biochemical Markers of Oxidative Stress in Aphids.

This study investigated the toxicity of essential oils (EOs) from Santolina chamaecyparissus (L.) and Tagetes patula (L.) towards the green peach aphid Myzus persicae (Sulzer) and the bird cherry-oat aphid Rhopalosiphum padi (L.). The effects of the EOs on aphid population parameters and levels of biochemical markers of oxidative stress within insect tissues were analyzed. In laboratory bioassays, application of the studied EOs at sublethal concentrations reduced daily fecundity and led to a decrease in the intrinsic rate of natural increase in both aphid species. Treatment with EOs also induced generation of reactive oxygen species (ROS) within aphid tissues. The highest levels of superoxide anion and hydrogen peroxide were noted after 24 and 48 h of exposure. Moreover, a significant increase in lipid peroxidation was shown in treated aphids, especially between 48 and 72 h after exposure. The increase was more pronounced after treatment with the essential oil of S. chamaecyparissus, which also exhibited higher aphicidal activity in toxicity tests. The activities of antioxidant enzymes-superoxide dismutase (SOD) and catalase (CAT)-were significantly elevated in both aphid species in response to the tested EOs. The obtained results suggest that oxidative stress evoked by treatment with the studied EOs may be an important factor determining their toxicity towards aphids.

Antimicrobial activity of five essential oils from lamiaceae against multidrug-resistant Staphylococcus aureus.

Analysis of Lamiaceae essential oils (EOs) by GC-FID-MS revealed the presence as the major constituents of linalool (16.8%), linalyl acetate (15.7%) in Lavandula angustifolia, menthol (29.0%), menthone (22.7%), menthyl acetate (19.2%) in Mentha x piperita, terpinen-4-ol (27.1%), (E)-sabinene hydrate (12.1%), γ-terpinene (10.0%) in Origanum majorana, α-thujone (19.5%), camphor (19.0%), viridiflorol (13.5%) in Salvia officinalis, thymol (61.9%), p-cymene (10.0%), γ-terpinene (10.0%) in Thymus vulgaris. Based on the MIC and MBC values (0.09-0.78 mg/mL) and ratio MBC/MIC showed that EO from T. vulgaris (TO) had the strong inhibitory and bactericidal effect against multidrug-resistant Staphylococcus aureus. The bacterial cells were total killed by TO at 2MIC concentration after 6 h. The higher concentrations of other EOs were needed to achieve bactericidal effects. The strong bactericidal effect of TO against these bacteria indicates the possibility of topical use of TO but it requires research under clinical conditions.

Transcriptional profiling of catalase genes in juglone-treated seeds of maize (Zea mays L.) and wheat (Triticum aestivum L.).

The major aim of the present study was to investigate the influence of juglone (JU; 5-hydroxy-1,4-naphthoquinone) treatments on the expression level of Cat1, Cat2 and Cat3 genes, encoding the respective catalase isozymes in maize (Zea mays L.) and wheat (Triticum aestivum L.) seeds. In parallel, germination efficiency, catalase (CAT) activity and hydrogen peroxide (H2O2) content in juglone-exposed cereal seeds were assessed. Juglone applications significantly stimulated abundance of three target catalase transcripts as well as induced CAT activity and generation of H2O2 in both maize and wheat kernels. Furthermore, germination process of juglone-affected maize seeds was more severe suppressed than in case of wheat kernels. The role of juglone in triggering the oxidative stress as well as antioxidative responses in seeds of the studied model cereal species are discussed.

Role of phenolic compounds during antioxidative responses of winter triticale to aphid and beetle attack.

One of the earliest responses of plants to insects' attack is generation of reactive oxygen species. However, the elevated level of ROS can elicit oxidative burst within plant tissues, and plants employ antioxidant systems against these radicals. Due to their chemical structures, polyphenols are able to diminish the level of ROS. Thus, we investigated the role of phenolic compounds in oxidative stress within winter triticale caused by Sitobion avenae and Oulema melanopus. It was found, that infestation by insects induced a high increase in the content of hydrogen peroxide and superoxide anion radical within resistant Lamberto cv. 24 hpi, whereas in sensitive Marko cv., an increase in H2O2 content was found within two days of aphid feeding. Moreover, resistant plants showed earlier and much greater induction of l-phenylalanine and l-tyrosine ammonia lyases and chalcone synthase activities, as well as accumulation of phenolic compounds in response to insect feeding than susceptible Marko. On the other hand, strong positive influence of hydrogen peroxide and superoxide radical contents on chalcone synthase activity and furthermore flavonoid biosynthesis was detected in the susceptible cultivar. Negative relationships between level of o-coumaric acid or flavonoid compounds and content of hydrogen peroxide or superoxide radical suggest their antioxidant capacity. Luteolin and o-coumaric acid may attend in scavenging of hydrogen peroxide, whereas quercetin, apigenin and (+)-catechin probably participate in reduction of superoxide anion radical content.

Coexistence of Borrelia burgdorferi s.l. genospecies within Ixodes ricinus ticks from central and eastern Poland.

The purpose of the study was to assess the prevalence and coinfection rates of Borrelia burgdorferi sensu lato genotypes in Ixodes ricinus (L.) ticks sampled from diverse localities in central and eastern regions of Poland. In years 2009-2011, questing nymphs and adults of I. ricinus were collected using a flagging method at 18 localities representing distinct ecosystem types: urban green areas, suburban forests and rural woodlands. Molecular detection of B. burgdorferi s.l. genospecies was based on amplification of a fla gene using nested PCR technique, subsequent PCR-RFLP analysis and bidirectional sequencing. It was revealed that 45 samples (2.1%) harboured two different B. burgdorferi s.l. genospecies, whereas triple infections with various spirochetes was found in 11 (0.5%) individuals. Generally, the highest average coinfection rates were evidenced in arachnids gathered at rural woodlands, intermediate at suburban forests, while the lowest were recorded at urban green areas. Overall, single spirochete infections were noted in 16.3% (n = 352/2,153) ticks. Importantly, it is the first report evidencing the occurrence of Borrelia miyamotoi (0.3%, n = 7/2153) in I. ricinus populations within central Poland. Circumstantial variability of B. burgdorferi s.l. genospecies in the common tick individuals sampled at various habitat types in central and eastern Poland was displayed. The coexistence of two or three different spirochete genospecies in single adult ticks, as well as the presence of B. miyamotoi were demonstrated. Therefore, further studies uncovering the co-circulation of the tested bacteria and other human pathogens in I. ricinus ticks are required.

Mechanism of entomotoxicity of the Concanavalin A in Rhopalosiphum padi (Hemiptera: Aphididae).

The toxicity effect of Concanavalin A (Canavalia ensiformis lectin, ConA) to bird cherry-oat aphid, Rhopalosiphum padi L. (Hemiptera: Aphididae), was investigated in the laboratory by using artificial diets containing ConA concentrations. Bird cherry-oat aphid performance was affected by the presence of Con A in artificial diets. The lectin added into the liquid diet increased the prereproductive period, mortality, and the average time of generation development (T) and decreased fecundity and the intrinsic rate of natural increase (rm). In attempt to unravel the mode of action of ConA, the interaction of the lectin with insect gut and the effect of ConA on feeding behavior were investigated. Extract of gut of treated grain aphid demonstrated DNA fragmentation, and this was accompanied with an increase in caspase 3 activity. Moreover, addition of ConA to the sucrose-agarose gels reduced salivation and passive ingestion of fluids from the gel. The results indicate that the insecticidal activity of ConA on R. padi may involve effects on death of the gut epithelial cells and effects on feeding behavior. This can be employed to create plants that are resistant to aphids.

Expression profiling of selected glutathione transferase genes in Zea mays (L.) seedlings infested with cereal aphids.

The purpose of this report was to evaluate the expression patterns of selected glutathione transferase genes (gst1, gst18, gst23 and gst24) in the tissues of two maize (Zea mays L.) varieties (relatively resistant Ambrozja and susceptible Tasty Sweet) that were colonized with oligophagous bird cherry-oat aphid (Rhopalosiphum padi L.) or monophagous grain aphid (Sitobion avenae L.). Simultaneously, insect-triggered generation of superoxide anion radicals (O2•-) in infested Z. mays plants was monitored. Quantified parameters were measured at 1, 2, 4, 8, 24, 48 and 72 h post-initial aphid infestation (hpi) in relation to the non-infested control seedlings. Significant increases in gst transcript amounts were recorded in aphid-stressed plants in comparison to the control seedlings. Maximal enhancement in the expression of the gst genes in aphid-attacked maize plants was found at 8 hpi (gst23) or 24 hpi (gst1, gst18 and gst24) compared to the control. Investigated Z. mays cultivars formed excessive superoxide anion radicals in response to insect treatments, and the highest overproduction of O2•- was noted 4 or 8 h after infestation, depending on the aphid treatment and maize genotype. Importantly, the Ambrozja variety could be characterized as having more profound increments in the levels of gst transcript abundance and O2•- generation in comparison with the Tasty Sweet genotype.

Biochemical characterisation of chlorophyllase from leaves of selected Prunus species--a comparative study.

Despite senescence-induced chlorophyll depletion in plants has been widely studied, the enzymatic background of this physiologically regulated process still remains highly unclear. The purpose of this study was to determine selected biochemical properties of partially purified fractions of chlorophyllase (Chlase, chlorophyll chlorophyllido-hydrolase, EC 3.1.1.14) from leaves of three Prunus species: bird cherry (Prunus padus L.), European plum (Prunus domestica L.), and sour cherry (Prunus cerasus L.). Secondarily, this report was aimed at comparing seasonal dynamics of Chlase activity and chlorophyll a (Chl a) content within investigated plant systems. Molecular weight of native Chlase F1 has been estimated at 90 kDa (bird cherry) and approximately 100 kDa (European plum and sour cherry), whereas molecular mass of Chlase F2 varied from 35 kDa (European plum) to 60 kDa (sour cherry). Furthermore, enzyme fractions possessed similar optimal pH values ranging from 7.6 to 8.0. It was found that among a broad panel of tested metal ions, Hg(+2), Fe(+2), and Cu(+2) cations showed the most pronounced inhibitory effect on the activity of Chlase. In contrast, the presence of Mg(+2) ions influenced a subtle stimulation of the enzymatic activity. Importantly, although Chlase activity was negatively correlated with the amount of Chl a in leaves of examined Prunus species, detailed comparative analyses revealed an incidental decrement of enzymatic activity in early or moderately senescing leaves. It provides evidence that foliar Chlase is not the only enzyme involved in autumnal chlorophyll breakdown and further in-depth studies elucidating this catabolic process are required.

Molecular screening for Bartonella henselae and Borrelia burgdorferi sensu lato co-existence within Ixodes ricinus populations in central and eastern parts of Poland.

The presented study aimed at establishing the prevalence and co-infection rates of Bartonella henselae and Borrelia burgdorferi sensu lato in Ixodes ricinus ticks collected from the central and eastern parts of Poland. The common tick individuals were gathered in the years 2008-2009. Questing ticks were sampled by dragging a white woollen flag over lower vegetation at 17 localities within diverse types of habitats: urban recreational green areas (city parks and squares), suburban forests and rural woodlands throughout the investigated regions of Poland. Detection of B. henselae in tested tick specimens was based on PCR amplification of the citrate synthase (gltA) gene, while screening for the presence of B. burgdorferi s.l. DNA was carried out by analyzing fragments of two genes: the flagellin (fla) and outer surface protein A (ospA). A total number of 1,571 I. ricinus ticks were sampled: 865 (55.1%) nymphs, 377 females (24.0%) and 329 males (20.9%). The application of PCR assays revealed that 76 (4.8%) tick samples were B. henselae-positive, B. burgdorferi s.l. DNA was detected in 194 specimens (12.3%), whereas the co-existence of these pathogens was evidenced in 22 tested ticks (1.4%). Furthermore, the occurrence of bartonellae and co-circulation of analysed microorganisms in I. ricinus was affirmed only within adult individuals, while presence of the screened spirochetes was ascertained in both nymphal and adult ticks. It should be stressed that the suburban woods of Warsaw and rural forests in Warsaw County characterized the highest prevalence levels of dual infection with investigated tick-borne pathogens, whereas the lowest co-infection rates were recorded in tick populations inhabiting rural forests in Plock County and forested areas in Korczew-Mogielnica (within the Nadbuzanski Landscape Park).

Molecular evidence of Anaplasma phagocytophilum and Babesia microti co-infections in Ixodes ricinus ticks in central-eastern region of Poland.

The aim of the study was to elucidate the distribution of Anaplasma phagocytophilum and Babesia microti co-infection in Ixodes ricinus populations within the central-eastern region of Poland. The prevalence of analysed tick-borne human pathogens in single and polymicrobial infections in I. ricinus ticks were analysed using the conventional and nested PCR techniques. A total number of 1,123 questing tick individuals (291 females, 267 males and 565 nymphs) were collected at different ecosystems (municipal parks, suburban forests, and woodlands). In the presented study, 95 samples of ticks (8.5%) were infected with A.phagocytophilum, 3.1% (n=35) with B. microti, whereas the co-existence status of these human pathogens was detected in 1.8% (n=20) of all tested samples. It has been demonstrated that the prevalence of co-infection status was the highest among females of I. ricinus (11 samples, 3.8%), whereas the lowest within tested nymphs (5 samples, 0.9%). Ticks collected at city parks in Warsaw and suburban areas of this town characterized the highest prevalence of co-infections (3.3 and 4.8%, respectively). Furthermore, it was established that co-infection rates of ticks inhabiting woodlands within Kampinos National Park and Nadbuzanski Landscape Park were similar and reached the levels of 1.4% (n=5) and 1.1% (n=4), respectively.