Nicotiana benthamiana as a model for studying Cryptococcus-plant interaction.

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. Cryptococcus gattii was able to grow in all three models, with a peak of yeast cell burden after 7 days, without any pathological effects. Furthermore, the fungal burden was reduced later, confirming that C. gattii is not a phytopathogen. Cryptococcus gattii proliferation was higher in N. benthamiana, which presented an increase in the hydrogen peroxide content, antioxidant system activity, and indoleacetic acid (IAA) production. Cryptococcus 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.

Cytological attributes of storage tissues in nematode and eriophyid galls: pectin and hemicellulose functional insights.

Cell walls and protoplast may work together or distinctly in the establishment of the functional profiles of gall tissue compartments. This presumption is herein evaluated in three gall systems by immunocytochemical and ultrastructural analyses. The common storage tissues (CSTs) of leaf galls induced by Eriophyidae on Miconia ibaguensis leaves and by Ditylenchus gallaeformans on M. ibaguensis and M. albicans have rigid and porous cell walls due to their composition of pectins. Hemicelluloses in CST cell walls are scarcer when compared to the cell walls of the control leaves, being functionally compensated by rigid pectate gels. The typical nutritive tissues (TNTs) in galls induced by Ditylenchus gallaeformans are similar to promeristematic and secretory cells regarding their enriched cytoplasm, several mitochondria, and proplastids, as well as multivesicular and prolamellar bodies in cell membranes. The cytological features of the feeding cells of Eriophyidae galls indicate that they are not as metabolically active as the cells of the TNT in nematode galls. However, their cell wall composition suggests more plasticity and porosity than the cells of the TNT, which can compensate the less production of nutrients with more transport. The ultrastructural and immunocytochemical profiles of CST cells reveal functional similarities, which are independent of the taxa of the gall inducer or of the host plant. Despite their analogous functionalities, the protoplast and cell wall features of TNT cells of nematode galls and of the feeding cells of the Eriophyidae galls are distinct, and work out through different strategies toward keeping gall developmental site active.