Which came first: The disease or the pest? Is there a host mediated spread of Beauveria bassiana (Ascomycota: Hypocreales) by invasive palm pests?

The red palm weevil (RPW) Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) is threatening the palm family worldwide, causing important economic losses. Current tactics to manage the weevil are largely based on chemical control, although the use of pesticides is hampered by several environmental constraints. Since the first introduction of RPW in Spain in 1996 and during its progressive spread around the Mediterranean basin, the number of reports of natural infection of RPW populations by entomopathogenic fungi (EPF) has been rising for 15 years, and this rise could support a pest-mediated EPF spread. To challenge this hypothesis, we assessed the usefulness of the region of elongation factor 1-alpha (EF1-α), Bloc nuclear intergenic region (Bloc) and inter simple sequence repeat (ISSR) markers, alone or in combination, to infer the relationships among Mediterranean Beauveria and Metarhizium strains isolated from the RPW. Second, the effect of abiotic factors, such as temperature, humidity and UV-B radiation, on the germination and growth of these EPFs strains as a function of their genealogy and geographic origin were determined. Finally, the pathogenicity of strains from different genetic clades was evaluated against larvae and adults of R. ferrugineus. The phylogenetic analysis based on the EF-1α gene identified eight different sequences among 24 fungal isolates of four fungal species. Similar clades were clustered when Bloc and ISSR analyses were performed. The results showed that strains of different origins were clustered in the same clade, and this outcome could be explained by an RPW-mediated EPF spread that was also influenced by time, geographical and other RPW related factors. Neither the response to abiotic factors nor virulence to RPW larvae and adults were related to the sequence type, with all B. bassiana strains well adapted to Mediterraneam climatic conditions. Taken together, these findings may help to select the best strain for RPW management.

Patterns of ambulatory dispersal in Tetranychus urticae can be associated with host plant specialization.

Dispersal can be an essential factor affecting the biological control of pests. Tetranychus urticae Koch (Acari: Tetranychidae) is a cosmopolitan and polyphagous species that may reach the pest status in many cropping systems including clementine orchards, where it may be found both in the trees and the associated flora. In a previous study, we demonstrated that the use of a ground cover of Festuca arundinacea Schreber (Poaceae) offered a better regulation of T. urticae populations than traditional alternatives (bare soil, multifloral wild cover). Therefore, we decided to study the ambulatory dispersal of mites crawling up and down tree trunks in a clementine mandarin orchard grown in association with a F. arundinacea cover for one season. The highest ambulatory migration rate was upward from the cover to the canopy. Multivariate regressions showed that the dynamics of T. urticae populations in the trees was strongly related to that of Phytoseiidae mites, their main natural predators. Surprisingly, canopy populations were not related to those on the ground cover or to those dispersing from it. When T. urticae individuals collected from the ground cover, the tree trunk, and the canopy were subjected to molecular analyses, the optimal number of genetic clusters (demes) was two. One clustergrouped individuals dispersed from the ground cover (e.g. collected on tree trunks) and 27.5% of individuals collected in the ground cover. The second cluster grouped all the individuals collected from trees and 72.5% of those collected in the cover. Interestingly, none of the individuals collected from the tree canopies was grouped with the first deme. This result may be taken as indicative that grass-adapted T. urticae individuals are unable to satisfactorily colonize and establish on the trees and provides evidence that host adaptation can hamper dispersal and establishment of the ground cover deme on trees, contributing to a better natural regulation of this pest species in citrus.

Activity of cholinesterases and adenosine deaminase in blood and serum of rats experimentally infected with Trypanosoma cruzi.

This study aimed to evaluate the activity of cholinesterases and adenosine deaminase (ADA) in blood and serum of rats infected with Trypanosoma cruzi. Twelve adult rats were used in the experiment divided into two uniform groups. Rodents from group A (control group) were non-infected and animals from group B served as infected, receiving intraperitoneally 3·3×10(7) trypomastigotes/each. Blood collection was performed at days 60 and 120 post-infection (PI) in order to evaluate the hemogram, blood activity of acetylcholinesterase, and serum butyrylcholinesterase and ADA activities. Hematological parameters did not differ between groups. A significant increase (P<0·05) of acetylcholinesterase activity was observed in blood while butyrylcholinesterase had a significant reduction (P<0·01) in serum of infected rats at days 60 and 120 PI. ADA activity in serum showed an inhibition in infected animals when compared to non-infected at day 120 PI. Based on these results, it is possible to conclude that the activity of cholinesterases and ADA were changed in animals infected with T. cruzi. The possible causes of these alterations will be discussed in this paper.

Biochemical characterization of adenosine deaminase (CD26; EC 3.5.4.4) activity in human lymphocyte-rich peripheral blood mononuclear cells.

The conversion of adenosine to inosine is catalyzed by adenosine deaminase (ADA) (EC 3.5.4.4), which has two isoforms in humans (ADA1 and ADA2) and belongs to the zinc-dependent hydrolase family. ADA modulates lymphocyte function and differentiation, and regulates inflammatory and immune responses. This study investigated ADA activity in lymphocyte-rich peripheral blood mononuclear cells (PBMCs) in the absence of disease. The viability of lymphocyte-rich PBMCs isolated from humans and kept in 0.9% saline solution at 4-8°C was analyzed over 20 h. The incubation time and biochemical properties of the enzyme, such as its Michaelis-Menten constant (Km) and maximum velocity (Vmax), were characterized through the liberation of ammonia from the adenosine substrate. Additionally, the presence of ADA protein on the lymphocyte surface was determined by flow cytometry using an anti-CD26 monoclonal human antibody, and the PBMCs showed long-term viability after 20 h. The ADA enzymatic activity was linear from 15 to 120 min of incubation, from 2.5 to 12.5 µg of protein, and pH 6.0 to 7.4. The Km and Vmax values were 0.103±0.051 mM and 0.025±0.001 nmol NH3·mg-1·s-1, respectively. Zinc and erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) inhibited enzymatic activity, and substrate preference was given to adenosine over 2'-deoxyadenosine and guanosine. The present study provides the biochemical characterization of ADA in human lymphocyte-rich PBMCs, and indicates the appropriate conditions for enzyme activity quantification.

Biochemical characterization of adenosine deaminase (CD26 EC 3. 5. 4. 4) activity in human lymphocyte-rich peripheral blood mononuclear cells

The conversion of adenosine to inosine is catalyzed by adenosine deaminase (ADA) (EC 3.5.4.4), which has two isoforms in humans (ADA1 and ADA2) and belongs to the zinc-dependent hydrolase family. ADA modulates lymphocyte function and differentiation, and regulates inflammatory and immune responses. This study investigated ADA activity in lymphocyte-rich peripheral blood mononuclear cells (PBMCs) in the absence of disease. The viability of lymphocyte-rich PBMCs isolated from humans and kept in 0.9% saline solution at 4-8°C was analyzed over 20 h. The incubation time and biochemical properties of the enzyme, such as its Michaelis-Menten constant (Km) and maximum velocity (Vmax), were characterized through the liberation of ammonia from the adenosine substrate. Additionally, the presence of ADA protein on the lymphocyte surface was determined by flow cytometry using an anti-CD26 monoclonal human antibody, and the PBMCs showed long-term viability after 20 h. The ADA enzymatic activity was linear from 15 to 120 min of incubation, from 2.5 to 12.5 µg of protein, and pH 6.0 to 7.4. The Km and Vmax values were 0.103±0.051 mM and 0.025±0.001 nmol NH3·mg-1·s-1, respectively. Zinc and erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) inhibited enzymatic activity, and substrate preference was given to adenosine over 2′-deoxyadenosine and guanosine. The present study provides the biochemical characterization of ADA in human lymphocyte-rich PBMCs, and indicates the appropriate conditions for enzyme activity quantification.