Nutrição e mecanismos do parasitismo de fungos do gênero Escovopsis
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Data
2019-02-25
Autores
Custodio, Bruna Cristina
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Universidade Estadual Paulista (Unesp)
Resumo
Em interações parasita-hospedeiro é esperado que o parasita obtenha a maior parte de sua nutrição a partir do hospedeiro. Colônias de formigas atíneas podem ser utilizadas como modelo para estudar diferentes mecanismos envolvidos em interações de parasitismo. Esses insetos cultivam um fungo basidiomiceto, o qual é alvo de micoparasitas do gênero Escovopsis. É sabido que o jardim de fungo, local onde as formigas praticam a fungicultura, apresenta uma alta concentração de fontes de carbono simples, de fácil assimilação. No presente estudo investigamos se o parasita se beneficia desses recursos nutricionais e se esses influenciam na infectividade frente ao hospedeiro. Para tanto, realizamos ensaios para avaliar o desenvolvimento de seis isolados de Escovopsis em diferentes fontes de carbono tanto na ausência, quanto na presença do fungo cultivado pelas formigas. Além disso, observamos a interação Escovopsis - fungo cultivado com microscopia de epifluorescência, a fim de verificar em que momento é iniciada a degradação do micélio do hospedeiro. No geral, o parasita apresentou esporulação abaixo de 59 % quando somente uma fonte simples de carbono estava disponível. Quando interagindo com seus hospedeiros em meio com apenas uma ou duas fontes de carbono, três dentre seis isolados do parasita foram menos infectivos do que o esperado. Observamos que a adição de uma fonte nutricional não aumenta a infectividade do parasita, mas influencia seu crescimento, mesmo na presença do hospedeiro (suposta fonte primária de nutrição). Nossos resultados sugerem que, além do micélio do hospedeiro, Escovopsis possa utilizar fontes adicionais de nutrientes presentes no jardim de fungo para seu desenvolvimento. Os ensaios com microscopia de epifluorescência evidenciaram que a degradação micelial do hospedeiro é iniciada antes do estabelecimento de contato físico entre as hifas, sugerindo a ação de metabólitos produzidos por Escovopsis.
In parasite-host interactions it is expected from the former to rely mostly on nutrients derived from the host. Attine ant colonies may be considered as a model system for studying different mechanisms of parasitism. These insects cultivate a basidiomycetous fungus, which is threatened by mycoparasites in the genus Escovopsis. It is known that the fungus garden, the substrate where the ants cultivate the fungal cultivar, has a high concentration of simple carbon sources. Here we investigated whether the parasite benefits from these nutritional resources and whether these nutrients influence host infectivity. We performed bioassays to evaluate the development of six Escovopsis isolates in different carbon sources in the absence as well as in the presence of the ant fungal cultivar. In addition, we observed the interaction Escovopsis – fungal cultivar with epifluorescence microscopy, to assess when the degradation of the host mycelium begins. Overall, the parasite showed sporulation below 59 % when only one carbon source was available. When interacting with their hosts in culture medium with one or two carbon sources, three out of six Escovopsis isolates were less infective than expected, probably due to nutritional stress. We observed that the parasite’s infectivity did not increase with the addition of one nutritional source, however, influenced its growth, even in the presence of the host (the expected primary source of nutrition). Our results suggest that in addition to the host mycelium, Escovopsis may use additional sources of nutrients present in the fungus garden for its development. Analysis with epifluorescence microscopy evidenced that the mycelial degradation of the host initiates before the establishment of physical contact between hyphae, suggesting that metabolites produced by Escovopsis are involved.
In parasite-host interactions it is expected from the former to rely mostly on nutrients derived from the host. Attine ant colonies may be considered as a model system for studying different mechanisms of parasitism. These insects cultivate a basidiomycetous fungus, which is threatened by mycoparasites in the genus Escovopsis. It is known that the fungus garden, the substrate where the ants cultivate the fungal cultivar, has a high concentration of simple carbon sources. Here we investigated whether the parasite benefits from these nutritional resources and whether these nutrients influence host infectivity. We performed bioassays to evaluate the development of six Escovopsis isolates in different carbon sources in the absence as well as in the presence of the ant fungal cultivar. In addition, we observed the interaction Escovopsis – fungal cultivar with epifluorescence microscopy, to assess when the degradation of the host mycelium begins. Overall, the parasite showed sporulation below 59 % when only one carbon source was available. When interacting with their hosts in culture medium with one or two carbon sources, three out of six Escovopsis isolates were less infective than expected, probably due to nutritional stress. We observed that the parasite’s infectivity did not increase with the addition of one nutritional source, however, influenced its growth, even in the presence of the host (the expected primary source of nutrition). Our results suggest that in addition to the host mycelium, Escovopsis may use additional sources of nutrients present in the fungus garden for its development. Analysis with epifluorescence microscopy evidenced that the mycelial degradation of the host initiates before the establishment of physical contact between hyphae, suggesting that metabolites produced by Escovopsis are involved.
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Palavras-chave
Nutrição microbiana, Parasita-hospedeiro, Infectividade, Resistência, Fungos filamentosos, Microbial nutrition, Parasite-Host, Infectivity, Resistance, Filamentous fungi