A fast and efficient method for preparation of high-quality RNA from fungal mycelia

BACKGROUND: Fungal RNA samples are usually isolated from fungal mycelia grown in liquid culture, which relies on prolific growth of the fungus in liquid media. The fungal biomass is then collected by vacuum filtration, which can result in low recovery for samples with reduced biomass due to poor growth in liquid media. FINDINGS: Here we report an alternative culturing method, based on growth on solid media which is independent of the ability of a fungus to grow in liquid culture. We show that growth on solid media overlayed with a nylon membrane is superior to other culturing methods, producing large amounts of biomass and allowing for easy harvesting of fungal mycelia. Furthermore, we show that mycelium harvested with this method yielded high-quality RNA, superior to RNA isolated from liquid grown mycelium. We also show that inclusion of a second chloroform extraction step in the procedure significantly increases RNA yield. CONCLUSIONS: This method is particularly useful for fungal species that show poor or no growth in liquid media, but are easily cultured on solid media. Culturing can be performed on small petri dishes, which significantly reduces handling and therefore allowing growth and isolation of RNA from multiple strains in a high throughput manner. The obtained RNA samples are of high quality in sufficient quantities for several northern blot experiments or quantitative RT-PCR experiments.