Effector-mediated communication of filamentous plant pathogens with their hosts

Pathogenic fungi and oomycetes can establish intimate associations with plants. These interactions underlie a molecular dialogue that leads to the successful colonization of host tissues. Major questions driving research in plant pathology these last decades are how pathogenic microorganisms circumvent preformed or induced defences and how pathogens manipulate host physiology to promote virulence. One key actor in this dialogue relies on a class of molecules secreted by pathogens termed effectors. Effectors perturb host processes by targeting a variety of host functions either in the apoplast or in the cytosol of host cells. This chapter focuses on fungal and oomycetal cytoplasmic effectors by reviewing methods to predict and to characterize effectors as well as their activities and role during infection. We provide current knowledge regarding their evolution and their putative role in the shaping of plant-associated microbial communities.