Symbiotic Fungus Of Leaf-cutting Ants Research Articles

<strong>Taxonomic and nomenclatural novelties in <em>Leucoagaricus</em> (Agaricaceae) from Brazil</strong>

Leucoagaricus nzumbae sp. nov. (Agaricaceae) is described based on morphological and molecular data from Teresópolis, Rio de Janeiro, Brazil. This species is characterized by the delicate small basidiomes that turn completely lilac when dried, brownish color of the pileus surface, and trichodermal elements with intracellular and parietal brown pigments of the pileus covering. A lectotype and an epitype are designated for Leucoagaricus gongylophorus, a symbiotic fungus of leaf-cutting ants. Full description, nomenclatural notes, and illustrations of fresh basidiomes in situ and of the main macro-and micromorphological features of both species are provided.

Extracts of Ageratum conyzoides, Coriandrum sativum and Mentha piperita inhibit the growth of the symbiotic fungus of leaf-cutting ants

Leaf-cutting ants live in symbiosis with the fungus Leucoagaricus gongylophorus (Singer) Möller that grows in their nests. This fungus is the main nutritional source for these ants that provide conditions for its development. Although plant extracts of Ageratum conyzoides L., Coriandrum sativum L. and Mentha piperita L. are known to cause mortality in ants in the laboratory, their effects on L. gongylophorus are still unknown. The aim of the present study was to determine the effects of the A. conyzoides, C. sativum and M. piperita extracts on L. gongylophorus. The biomass of the fungus grown by the leaf-cutting ants was assessed in culture medium with three concentrations (25, 50, and 100mg/mL) of A. conyzoides, C. sativum and M. piperita extracts. The results showed that all the three extracts inhibited the growth of L. gongylophorus. At concentrations of 25, 50, and 100mg/mL, the A. conyzoides extract exhibited 81, 93, and 100% reduction in the fungal biomass; the C. sativum extract showed 23, 27, and 100% reduction in the fungal biomass; and the M. piperita extract demonstrated 96, 99, and 100% reduction in the fungal biomass, respectively. Furthermore, the secondary metabolic compounds of these plants were found to have fungistatic and fungicidal properties, similar to that observed in other fungal species. In conclusion, the extracts of A. conyzoides, C. sativum and M. piperita inhibited the growth of L. gongylophorus in the laboratory, and should be further studied for their potential use in baits to control leaf-cutting ants.

Starch metabolism in Leucoagaricus gongylophorus, the symbiotic fungus of leaf-cutting ants

Leucoagaricus gongylophorus, the symbiotic fungus of the leaf-cutting ants, degrades starch, this degradation being supposed to occur in the plant material which leafcutters forage to the nests, generating most of the glucose which the ants utilize for food. In the present investigation, we show that laboratory cultures of L. gongylophorus produce extracellular alpha-amylase and maltase which degrade starch to glucose, reinforcing that the ants can obtain glucose from starch through the symbiotic fungus. Glucose was found to repress alpha-amylase and, more severely, maltase activity, thus repressing starch degradation by L. gongylophorus, so that we hypothesize that: (1) glucose down-regulation of starch degradation also occurs in the Atta sexdens fungus garden; (2) glucose consumption from the fungus garden by A. sexdens stimulates degradation of starch from plant material by L. gongylophorus, which may represent a mechanism by which leafcutters can control enzyme production by the symbiotic fungus. Since glucose is found in the fungus garden inside the nests, down-regulation of starch degradation by glucose is supposed to occur in the nest and play a part in the control of fungal enzyme production by leafcutters.

A New Imidazole Alkaloid and Other Constituents from Pilocarpus grandiflorus and their Antifungal Activity

The stems of Pilocarpus grandiflorus have afforded the new imidazole alkaloid 4,6-dehydro- 1,2,4,5-tetrahydro-2,5-dioxopilocarpine in addition to the 17 known compounds germanicol, β - amiryn, ocotillone, stigmast-4-en-3-one, 3β -hydroxy-stigmast-5-en-7-one, 6β -hydroxy-stigmast-4- en-3-one, β -sitosterol, scopoletin, 3-(1’,1’-dimethylallyl)-scopoletin, elisin, dictamine, 4-methoxy-2- quinolone, platydesmine, syringaresinol, syringaldehyde, syringic acid and vanillic acid. Their structures were elucidated on the basis of chemical and spectroscopic evidence. The phenolic compounds vanillic acid and syringaldehyde and the furoquinoline alkaloid platydesmine exhibited antifungal activity against Leucoagaricus gongylophorus, the symbiotic fungus of leaf-cutting ants (Atta sexdens rubropilosa).

Inhibition of the symbiotic fungus of leaf-cutting ants by coumarins

Leaf-cutting ants are known to be a serious pest for agriculture due to the high amounts of vegetal matter from crops used by them in order to cultivate a symbiotic fungus on which they rely for food and enzymes. The mutualism between the fungus and the ants is a point to be explored when alternative methods of control are being thought of. Considering that some plants are naturally resistant to phytophagous insects, some natural products (secondary metabolites) should be evaluated with respect to their insecticide and/or fungicide properties. In this paper we isolated eight coumarins from four different plant species and we determined their effect on the development of the symbiotic fungus of the leaf-cutting ant Atta sexdens. With the exception of clausarin, all the other coumarins were inhibitory from 64 µg mL-1 through 80 µg mL-1 and xanthyletin inhibited the fungus at 25 µg mL-1

Random Amplified Polymorphic DNA Markers Reveal Genetic Variation in the Symbiotic Fungus of Leaf-Cutting Ants

RAPD markers were used to examine the degree of genetic variation within the putatively asexual basidiomycete fungus (Lepiotaceae: provisionally named Leucoagaricus gongylophorus) associated with the leaf-cutting ant species Atta cephalotes. We analyzed fungal isolates from ant nests in two geographically distant sites, two isolates from Panama and five isolates from Trinidad. Ten decamer primers were used to amplify total DNA from these seven fungal isolates, and RAPD banding patterns were compared. Genetic similarity among isolates was determined by pair-wise comparisons of the shared number of DNA bands on an agarose gel. There was considerable genetic variation among isolates of the symbiotic fungus even within sites. Pairs of fungal isolates from the two different sites shared an average of only 36% of the bands in their RAPD profiles, while pairs from the within sites shared an average of 72% of the bands. RAPD markers may be useful for further investigation of the genetic structure of the fungal symbiont within species of leaf-cutting ants.

Biological Activity of Quinoline Alkaloids from Raulinoa echinata and X-ray Structure of Flindersiamine

Phytochemical survey of stems and leaves extracts of the South Brazilian endemic plant Raulinoa echinata Cowan, Rutaceae, led to the isolation of known furoquinoline alkaloids: the widespread skimmianine; kokusaginine, maculine, flindersiamine, and also quinolone derivatives: 1-methyl-2-n-nonyl-4-quinolone, 2-n-nonyl-4-quinolone and 1-methyl-2-phenyl-4-quinolone. These alkaloids showed antifungal activity against Leucoagaricus gongylophorus; the symbiotic fungus of leaf-cutting ants (Atta sexdens). They were inactive or displayed weak inhibitory activity when assayed in vitro against trypomastigote forms of Trypanosoma cruzi. In this paper, the isolation, structure elucidation and bioactivity results of these compounds are reported together with the X-ray structure of flindersiamine.

RAPD analysis of the sexual state and sterile mycelium of the fungus cultivated by the leaf-cutting ant Acromyrmex hispidus fallax

That the symbiotic fungus of leaf-cutting ants only occasionally produces the sexual phase makes their identification confusing. This has occurred so rarely, either in laboratory nests, or in unbalanced field nests, that the possibility of contamination of the fungal garden by other fungi cannot be disregarded. In this paper we describe the formation of several basidiomata in a healthy and free-living nest of the leaf-cutting ant Acromyrmex hispidus fallax the cultivation in vitro of the sterile mycelia (isolated from the fungal garden) with their typical inflated tips, and the similarity of both forms confirmed by RAPD analysis of their genomic DNA. The fungus was identified as Leucoagaricus gongylophorus.

Toxicity of lignans to symbiotic fungus of leaf-cutting ants

Lignans fromVirola sebifera Aubl.,Virola sp., andOtoba parvifolia (Mkfg.) A. Gentry (Myristicaceae) inhibited the in vitro growth of the fungus cultivated by leaf-cutting ants of the speciesAtta sexdens rubropilosa Forel (Hymenoptera: Formicidae). A comparison of activity among the lignans was obtained.

Toxicity of sesame extracts to the symbiotic fungus of leaf-cutting ants

AbstractExtracts of different sesame plant (Sesamum indicum) Linnaeus organs inhibited the in vitro growth of the fungus Leucocoprinus gongylophorus (Möller) (=Rozites gongylophora Möller), which is cultivated by the leaf-cutting ants of the species Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae). The presence of the factor responsible for this inhibition was detected in methanol or chloroform extracts and is constant in the plant.