Distinct vacuolar responses to salinity stress in the hyphal cell of salt-tolerant and salt-sensitive strains of Rhizopogon roseolus.

The vacuole is a highly dynamic organelle that can change its morphology in response to environmental conditions. In this study, we investigated the vacuolar dynamics in the terminal and subterminal hyphal cells of ectomycorrhizal fungi Rhizopogon roseolus under saline stress using a microscopic approach with artificial seawater. Terminal cells responded to seawater exposure by increasing spherical vacuole formation. Artificial seawater induced progressive vacuolar fragmentation in subterminal cells of salt-sensitive strains. In contrast, the salt-tolerant strain exhibited a distinct adaptive response characterized by an increase in average vacuolar size following the initial salt shock. These findings reveal that strain-specific differences in vacuolar dynamics contribute to contrasting growth abilities under saline conditions and highlight the vacuole as a central organelle in the salt adaptation of ectomycorrhizal fungi.