Metabolism of Plant Polysaccharides by
            <i>Leucoagaricus gongylophorus</i>
            , the Symbiotic Fungus of the Leaf-Cutting Ant
            <i>Atta sexdens</i>
            L

Siqueira, Celia Gomes de; Bacci, Maurício; Pagnocca, Fernando Carlos; Bueno, Odair Corrêa; Hebling, M. J. A.

doi:10.1128/aem.64.12.4820-4822.1998

Cited by 55 publications

(25 citation statements)

References 23 publications

(21 reference statements)

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“…These results support the hypothesis that leaf‐cutting ant gardens primarily use the protein and starch of the fresh leaf substrate that the ants provide (Abril and Bucher 2004; Silva et al 2006a), and invest relatively less in degrading the structural cell wall components except for partial pectin degradation to facilitate access to the inner plant cell contents. This is consistent with in vitro garden cultures of leaf‐cutting ant fungi growing faster and producing more enzymes on starch than on cellulose substrates (Gomes de Siqueira et al 1998; Silva et al 2006b). Similar growth tests have not been done systematically with lower‐attine cultivars.…”

Section: Discussionsupporting

confidence: 84%

Evolutionary Transitions in Enzyme Activity of Ant Fungus Gardens

et al. 2010

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Fungus-growing (attine) ants and their fungal symbionts passed through several evolutionary transitions during their 50 millionyear old evolutionary history. The basal attine lineages often shifted between two main cultivar clades, whereas the derived higher-attine lineages maintained an association with a monophyletic clade of specialized symbionts. In conjunction with the transition to specialized symbionts, the ants advanced in colony size and social complexity. Here we provide a comparative study of the functional specialization in extracellular enzyme activities in fungus gardens across the attine phylogeny. We show that, relative to sister clades, gardens of higher-attine ants have enhanced activity of protein-digesting enzymes, whereas gardens of leaf-cutting ants also have increased activity of starch-digesting enzymes. However, the enzyme activities of lower-attine fungus gardens are targeted primarily toward partial degradation of plant cell walls, reflecting a plesiomorphic state of nondomesticated fungi. The enzyme profiles of the higher-attine and leaf-cutting gardens appear particularly suited to digest fresh plant materials and to access nutrients from live cells without major breakdown of cell walls. The adaptive significance of the lower-attine symbiont shifts remains unclear. One of these shifts was obligate, but digestive advantages remained ambiguous, whereas the other remained facultative despite providing greater digestive efficiency.

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Section: Discussionsupporting

confidence: 84%

Evolutionary Transitions in Enzyme Activity of Ant Fungus Gardens

et al. 2010

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“…The extent to which the acquisition of herbivorous lifestyles has depended on acquisition of foreign genes is thus still unclear. of plant polymers, potentially from a diverse array of host plant polymer types (Gomes De Siqueira et al 1998;D'Ettorre et al2002;Richard et al 2005;Silva et al2006a,b;Schiøtt et al 2008;Erthal et al 2009;De Fine Licht et al 2010;Kooij et al 2011). Some plant biomass degradation enzymes are upregulated in the specialized gongylidia located in the middle of the garden, where ants feed.…”

Section: Box 2 the Role Of Horizontal Gene Transfer In Enabling Insecmentioning

confidence: 99%

The impact of microbial symbionts on host plant utilization by herbivorous insects

2013

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Herbivory, defined as feeding on live plant tissues, is characteristic of highly successful and diverse groups of insects and represents an evolutionarily derived mode of feeding. Plants present various nutritional and defensive barriers against herbivory; nevertheless, insects have evolved a diverse array of mechanisms that enable them to feed and develop on live plant tissues. For decades, it has been suggested that insect-associated microbes may facilitate host plant use, and new molecular methodologies offer the possibility to elucidate such roles. Based on genomic data, specialized feeding on phloem and xylem sap is highly dependent on nutrient provisioning by intracellular symbionts, as exemplified by Buchnera in aphids, although it is unclear whether such symbionts play a substantive role in host plant specificity of their hosts. Microorganisms present in the gut or outside the insect body could provide more functions including digestion of plant polymers and detoxification of plant-produced toxins. However, the extent of such contributions to insect herbivory remains unclear. We propose that the potential functions of microbial symbionts in facilitating or restricting the use of host plants are constrained by their location (intracellular, gut or environmental), and by the fidelity of their associations with insect host lineages. Studies in the next decade, using molecular methods from environmental microbiology and genomics, will provide a more comprehensive picture of the role of microbial symbionts in insect herbivory.

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“…Evidence supporting cellfulose digestion by the fungus come from a few studies based on laboratory cultures on cellulose media (Martin & Weber 1969; Bacci et al . 1995; Gomes de Siqueira et al . 1998) and from the observed differences in cellulose content between the fungus garden and the refuse material (Martin & Weber 1969).…”

Section: Introductionmentioning

confidence: 83%

“…In our opinion, the modest fungus growth in cellulose media previously reported in the literature (Martin & Weber 1969; Bacci et al . 1995; Gomes de Siqueira et al . 1998) may be due to the presence of small amounts of alternative carbon sources in the culture media, particularly growth factors and impurities in the cellulose source.…”

Section: Discussionmentioning

confidence: 99%

“…However, the following facts suggest that the available evidence is not conclusive: (1) although all previous studies concluded that cellulose was degraded by the fungus, their results showed that fungus growth in cellulose media was limited (Martin & Weber 1969; Bacci et al . 1995; Gomes de Siqueira et al . 1998); (2) the material dumped by the leaf‐cutting ants had a high proportion of easily recognizable plant fragments (Jonkman 1977), not expected in plant material supposedly attacked by cellulolytic fungi (Paul & Clark 1996); and (3) unlike termites, leaf‐cutting ants never forage on paper (Quinlan & Cherrett 1977; Shepherd 1982).…”

Section: Introductionmentioning

confidence: 99%

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Evidence that the fungus cultured by leaf‐cutting ants does not metabolize cellulose

Abril

Bucher

2002

Ecology Letters

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Leaf-cutting ants are a very specialized group of ants that cultivate fungus gardens in their nests, from which they obtain food. The current opinion is that the fungus cultivated by leaf-cutting ants digests cellulose. Here we reassess the cellulose-degrading capability of the fungus by using two complementary approaches tested in four Attini species (genera Atta and Acromyrmex): (1) ability of fungus to grow in cellulose; and (2) lignin/cellulose ratio in the refuse material dumped outside the nest, as an indicator of cellulose consumption. We found that (1) the fungus did not grow in cellulose, and (2) the lignin/cellulose ratio was much lower in the ants' refuse than in material digested by cellulose-digesting organisms, such as brown-rot fungus, termites, and ruminant mammals. This evidence strongly suggests the inability of the fungus to degrade cellulose. Therefore, the fungus-ant symbiosis and the ecological role of leaf-cutting ants need to be reconsidered.

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Metabolism of Plant Polysaccharides by Leucoagaricus gongylophorus , the Symbiotic Fungus of the Leaf-Cutting Ant Atta sexdens L

Cited by 55 publications

References 23 publications

Evolutionary Transitions in Enzyme Activity of Ant Fungus Gardens

Evolutionary Transitions in Enzyme Activity of Ant Fungus Gardens

The impact of microbial symbionts on host plant utilization by herbivorous insects

Evidence that the fungus cultured by leaf‐cutting ants does not metabolize cellulose

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