Nicotiana benthamiana as a model for studying Cryptococcus–plant interaction

Abstract

Cryptococcus gattii, an environmental yeast isolated from plants, is one of the agents of cryptococcosis. Here we aimed to develop a plant model to study C. gattii-plant interaction since it is unclear how it affects the plant and the yeast. We tested three inoculation methods (scarification, infiltration, and abrasion) in three plant species: Arabidopsis thaliana, Nicotiana tabacum, and N. benthamiana. C. gattii was able to grow in all three models, with a peak of yeast cell burden after seven days, without any pathological effects. Furthermore, the fungal burden was reduced later, confirming that C. gattii is not a phytopathogen. C. gattii proliferation was higher in N. benthamiana, which presented an increase in the hydrogen peroxide content, antioxidant system activity, and indoleacetic acid (IAA) production. C. gattii colonies recovered from N. benthamiana presented lower ergosterol content, reduced capsule, and increased growth rate in vitro and inside macrophages. In vitro, IAA altered C. gattii morphology and susceptibility to antifungal drugs. We hypothesize that C. gattii can temporarily colonize plant living tissues, which can be a potential reservoir of yeast virulence, with further dissemination to the environment, birds, and mammals. In conclusion, N. benthamiana is suitable for studying C. gattii-plant interaction.

A fungal lytic polysaccharide monooxygenase is required for cell wall integrity, thermotolerance, and virulence of the fungal human pathogenCryptococcus neoformans

“…Supp Fig 3C illustrates the absence of pathological signs 7 days after drop inoculation, as well as scanning electron microscopy images of the C. neoformans cells failing to penetrate the leaf surface in its yeast form. These results demonstrate resistance of mature, soil-grown plants to C. neoformans infection, in agreement with recent results from Dornelas and colleagues [36], who also saw no plant phenotypes after Cryptococcus inoculation. These observations did not demonstrate a definitive role for Cn Cel1 for plant penetration in this model.…”

A fungal lytic polysaccharide monooxygenase is required for cell wall integrity, thermotolerance, and virulence of the fungal human pathogen Cryptococcus neoformans

“…Prior investigations in C . neoformans have reported varying degrees of association with live plants, despite frequent isolation of this fungus from decaying plant material [ 34 ]. Using previously described methods of Cryptococcus – Arabidopsis thaliana co-incubation models [ 35 – 38 ], we observed no differences in plant association between WT, cel1 Δ, and cel1 Δ C strains by scanning electron microscopy of the plant surface ( S3C Fig ).…”

“…In plant pathogenic fungal species, LPMO's have been proposed to promote the establishment of infection on the plant surface by degrading structural polysaccharides such as lignocellulose [15,33]. Prior investigations in C. neoformans have reported varying degrees of association with live plants, despite frequent isolation of this fungus from decaying plant material [34]. Using previously described methods of Cryptococcus-Arabidopsis thaliana co-incubation models [35][36][37][38], we observed no differences in plant association between WT, cel1Δ, and cel1Δ C strains by scanning electron microscopy of the plant surface (S3C Fig).…”