Patch clamp pipette giga seal forming success on the nanosurgery-obtained filamentous fungi protoplasts

Abstract

The success of patch-clamp giga-ohm seal formation on filamentous fungi Phycomyces blakesleeanus protoplasts was investigated to evaluate their usefulness in ion channel studies on filamentous fungi. Protoplasts were obtained by laser-mediated nanosurgery of the cell wall stained with Calcofluor White. To enable a successful seal formation, it is critical to prevent cell wall regeneration. Since wall integrity responses in fungi involve kinase-dependent pathways, we aimed to sufficiently reduce intracellular ATP availability using the respiratory inhibitor azide. The effect of azide on phosphate metabolites of Phycomyces blakesleeanus, as determined by 31P NMR spectroscopy, was a reduction in intracellular ATP accompanied by a decrease in long chain polyphosphates. Subsequently, all seal formation measurements were performed in the presence of azide, and protoplast viability was confirmed by cytoplasmic streaming. The success of seal formation depends on the size of the protoplasts, as larger protoplasts are more prone to successful seal formation. It was also found that the laser power used in nanosurgery could influence the success of seal formation, as higher values were associated with a lower success rate. The protoplasts released by laser nanosurgery produced by our newly developed method are a good model system for patch clamp on filamentous fungal membranes because their plasma membrane can easily form high-quality seals with the patch pipette.