Standardized Conditions to Study Beneficial and Nonbeneficial Traits in the Piriformospora indica/Arabidopsis thaliana Interaction

Abstract

The vast majority of plants live in symbiotic interaction with mycorrhizal fungi. The fungus delivers soil nutrients to the plant (Javot et al. 2007a, b; Bucher et al. 2009; Adesemoye and Kloepper 2009) while the plant is responsible for the photoassimilates to the fungus (Nehls 2008; Nehls et al. 2010). Mycorrhizal interactions are difficult to investigate at the molecular level because most of the classical model plants do not form mycorrhizal association. As an alternative, endophytic interaction of axenically cultivable Piriformospora indica with the model plant Arabidopsis thaliana might help to understand the basis of the beneficial interactions between two symbionts. We focus on the identification of Arabidopsis mutants which are impaired in establishing or maintaining the interaction in a beneficial mode. For those studies, reproducible and quantitative cocultivation parameters are required. Therefore, we have developed standardized (co)cultivation conditions for the two symbionts, which are described here in details. The mode of interaction and the reproducibility of the data are highly dependent on the quality of the biological material and the cocultivation conditions. Most important parameters are the age and the density of the fungal mycelium, the age of the seedlings and plants, the ratio between the two symbiotic partners, and the cocultivation conditions like temperature, humidity, light intensity, spectral distribution, and photoperiod (Shahollari et al.