Isolated and Community Contexts Produce Distinct Responses by Host Plants to the Presence of Ant-Aphid Interaction: Plant Productivity and Seed Viability

<div><p>Ant-aphid interactions may affect host plants in several ways, however, most studies measure only the amount of fruit and seed produced, and do not test seed viability. Therefore, the aim of this study was to assess the effects of the presence of ant-aphid interactions upon host plant productivity and seed viability in two different contexts: isolated and within an arthropod community. For this purpose we tested the hypothesis that in both isolated and community contexts, the presence of an ant-aphid interaction will have a positive effect on fruit and seed production, seed biomass and rate of seed germination, and a negative effect on abnormal seedling rates, in comparison to plants without ants. We performed a field mesocosm experiment containing five treatments: Ant-aphid, Aphid, Community, Ant-free community and Control. We counted fruits and seeds produced by each treatment, and conducted experiments for seed biomass and germinability. We found that in the community context the presence of an ant-aphid interaction negatively affected fruit and seed production. We think this may be because aphid attendance by tending-ants promotes aphid damage to the host plant, but without an affect on seed weight and viability. On the other hand, when isolated, the presence of an ant-aphid interaction positively affected fruit and seed production. These positive effects are related to the cleaning services offered to aphids by tending-ants, which prevent the development of saprophytic fungi on the surface of leaves, which would cause a decrease in photosynthetic rates. Our study is important because we evaluated some parameters of plant fitness that have not been addressed very well by other studies involving the effects of ant-aphid interactions mainly on plants with short life cycles. Lastly, our context dependent approach sheds new light on how ecological interactions can vary among different methods of crop management.</p></div

Plants production (fruits and seeds) per treatment.

<p>Produced fruits (A) and seeds (B) for the treatments: Control—caged plants without ant-aphid interaction, and exclusion of all the arthropods from the plant; Aphid–caged plants infested by aphids, and exclusion of others arthropods, including ants; Ant-aphid–caged plants with the presence of the ant-aphid interaction only, and exclusion of other arthropods; Communit<b>y</b>–cageless plants with free access to the entire arthropod community; and Ant free community–plants with ant exclusion.</p

Traits and viability of seeds produced.

<p>Seed biomass (A) and number of abnormal seedlings (B) for the treatments: Control—caged plants without ant-aphid interaction, and exclusion of all the arthropods from the plant; Community–cageless plants with free access to the entire arthropod community; and Ant free community–plants with ant exclusion. The isolated treatments Aphid and Ant-aphid did not produce seed amount enough to seed traits experiments.</p

Benzimidazole inhibitors of the major cysteine protease of Trypanosoma brucei

Limitations in available therapies for trypanosomiases indicate the need for improved medicines. Cysteine proteases cruzain and rhodesain are validated targets for treatment of Chagas disease and human African trypanosomiasis. Previous studies reported a benzimidazole series as potent cruzain inhibitors. Results & methodology: Considering the high similarity between these proteases, we evaluated 40 benzimidazoles against rhodesain. We describe their structure-activity relationships (SAR), revealing trends similar to those observed for cruzain and features that lead to enzyme selectivity. This series comprises noncovalent competitive inhibitors (best K-i = 0.21 mu M against rhodesain) and micromolar activity against Trypanosoma brucei brucei. A cheminformatics analysis confirms scaffold novelty, and the inhibitors described have favorable predicted physicochemical properties. Conclusion: Our results support this series as a starting point for new human African trypanosomiasis medicines111315371551sem informaçã