Downy mildew infection of Arabidopsis.
Haustoria of the downy mildew pathogen Hyaloperonospora arabidopsidis are progressively encased with callose-rich materials by the host. In this image, the callose in an infected leaf has been stained by aniline blue, tracing the path of the encasement response along the length of the pathogen hyphae. Marie-Cécile Caillaud and colleagues have identified a novel component of the mechanism by which callose is deposited in these encasements, positively regulating host defence.
Image Credit: Marie-Cécile Caillaud and Sophie Piquerez