Getting the Most from the Host: How Pathogens Force Plants to Cooperate in Disease

Plant diseases caused by pathogenic microorganisms remain a major limitation in many crop production systems. Nonetheless, constitutive and inducible defense mechanisms render most plants inaccessible to pathogens, making disease an exception rather than a common outcome of plant-microbe interactions. Defense mechanisms and associated pathogen resistance were thus of key interest to many plant pathologists, and many of the molecular mechanisms underlying resistance have been elucidated over the last few decades. In recent years, the analysis of physiological and molecular determinants accounting for successful infection and eventual disease has become a topic of prime scientific interest. The hunt is now on for pathogen effectors subverting the host cell and for the plant compatibility functions manipulated by these effectors. An understanding of the molecular mechanisms underlying successful infection should make it possible to develop new crop protection strategies based on interference with compatibility to prevent disease. This review is addressing plant susceptibility and highlights a number of host processes that have been shown to be induced or subverted to facilitate infection. In particular, we focus on those processes that appear to be manipulated by filamentous fungal and oomycete pathogens.