Chemical and molecular studies of ant-bacterial-fungus interactions

• Grant number: 19/19833-9
• Support Opportunities: Research Grants - Visiting Researcher Grant - International
• Duration: November 07, 2019 - November 13, 2019
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Organic Chemistry
• Principal Investigator: João Batista Fernandes
• Grantee: João Batista Fernandes
• Visiting researcher: Ludger Aloisius Wessjohann
• Visiting researcher institution: Leibniz Institute of Plant Biochemistry (IPB), Germany
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 12/25299-6 - Integrated studies for leaf cutting control, AP.TEM

Abstract

Ludger Aloisius Wessjohann (Department of Bioorganic Chemistry, Leibniz Institute of Plant Biochemistry, Halle, Germany) works on the development of bioactive compounds using medicinal, food and agricultural chemistry. He recently published a study of Tapinoma ants of the subfamily Dolichoderinae, family Formicidae, which produce a variety of volatile compounds such as chemical defense, alarm and pheromones of communication. In this work they determined and characterized the chemical profile of pheromones and volatile compounds of two Tapinoma species. We have been working with ants for years and our theme is "Integrated Studies for the Control of Leaf Ants". These ants collect fresh leaves to grow the symbiotic fungi that serve as the basis for feeding the colony. The genus Atta (Hymenoptera: Formicidae) stands out for its economic importance due to its destructive power of a large number of plant species causing direct and indirect economic damage to agriculture, pasture and forestry. The most efficient method for controlling leaf-cutting ants is chemical control which, in most cases, is non-selective and can harm human health and the environment. We recently reported for the first time the isolation of two Atta sexdens AChEs that were purified by ammonium sulfate precipitation followed by ion exchange chromatography. Enzymes AsAChE-A and AsAChE-B have an optimal pH of 9.5 and 9.0 and higher activities at 30/50 °C and 20 °C, respectively, using acetylthiocholine (ATCh) as substrate. Immobilized capillary enzyme reactors (ICERs) were obtained for both enzymes (AsAChE-A-ICER and AsAChE-B-ICER) and their activities were measured by LC-MS/MS by quantifying the natural substrate of ACh hydrolysis. Comparison of LC-MS/MS activities of both AChEs using ACh as substrate showed that AsAChE-B (free or immobilized) had the highest affinity. The inverse result was observed when the colorimetric assay (Elman method) was used for ATCh as substrate. In addition, by mass spectrometry and phylogenetic studies, AsAChE-A and AsAChE-B were classified as belonging to classes AChE-2 and AChE-1, respectively. These enzymes are important for direct action mechanism assays with leaf-cutting ants. We could cite several other works to show the great interest in close interaction with Ludger A. Wessjohann. See the proposed program attached, which will lead to this interaction and future student exchanges. (AU)