Detection of Arbuscular Mycorrhizal Fungal Gene Expression by In Situ Hybridization

Abstract

The complexity of the obligate symbiotic interaction of arbuscular mycorrhizal (AM) fungi and their host roots requires sophisticated molecular methods. In particular, to capture the dynamic of the interaction, cell-specific methods for gene expression analysis are required. In situ hybridization is a technique that allows to determine the location of transcript accumulation within tissues, being of special interest for these fungi that cannot be genetically modified. The method requires proper fixation and embedding methods as well as specific probes for the hybridization allowing detection of specific transcripts. In this chapter, we present a method to prepare roots, which have established a symbiosis with an arbuscular mycorrhizal fungus for the detection of fungal transcripts. This includes chemical fixation, subsequent embedding in a suitable medium, sectioning and pretreatment of sections, the hybridization procedure itself, as well as the immunological detection of RNA-RNA hybrids.