Fig. 6

Confocal laser scanning micrographs of fungus–plant cell interaction between Polydomus karssenii strain DSM 106825 and wheat. Wheat seedlings (1 week old) were inoculated with mycelium plugs and infection monitored 8–9 weeks thereafter. Infected plant roots were treated with aniline blue diammonium salt to stain fungal and plant cell wall “β-glucans" (overlay of stain and autofluorescence of cytoplasm depicted in yellow, or orange pseudo colours, respectively) and wheat germ agglutinin-Alexa Fluor 488 (WGA-AF488) to stain fungal chitin (blue/turquoise pseudo colour). a–c General view of root apex showing fungal colonisation. d Transverse section of root showing intercellular colonisation of root cells by strain DSM 106825. e Transverse section of vascular cylinder (stele) showing that the fungus colonised cortex and endodermal cells but not the vascular tissues. f Longitudinal section showing hyphal swelling, resembling an appressorium, and formation of a penetration peg surrounded by a callosic papilla-like structure. g, h Longitudinal section showing the development of callosic papilla-like structures surrounding hyphal penetration pegs. i Transverse section showing intercellular colonisation of the fungus and formation of callostic papilla-like structures associated with the fungal colonisation of plant cells. j Longitudinal section indicating the growth of a hypha by passing through callosic tissues (papillae like structures). Bars = 50 µm (a–c), 10 µm (d–j)