Hyaloperonospora arabidopsidis: A model pathogen of Arabidopsis

Abstract

Hyaloperonospora arabidopsisdis (Hpa) is a naturally occurring pathogen of the reference plant Arabidopsis thaliana, upon which it causes downy mildew disease. Hpa has been utilized since the late 1980s as a model pathogen of Arabidopsis to elucidate fundamental aspects of plant-oomycete interactions. Hpa is also a model for obligate biotrophic pathogens that cannot exist apart from their hosts, and for downy mildew pathogens that cause destructive diseases of crops. The recently sequenced genome of Hpa isolate Emoy2 has opened the door to deeper understanding of many aspects of plant-oomycete interactions, most notably the first genome-level insights into the molecular basis and evolution of the obligate biotrophy. Additionally, bioinformatic screens of the Hpa genome have identified a large collection of virulence genes (e.g., RxLR effectors). Functional analyses of these genes, along with the experimental tools of Arabidopsis, is already providing new insights into the mechanisms through which oomycetes manipulate host cells. These and other applications of data from the Hpa genome will ultimately translate into new strategies to control downy mildew and other oomycete diseases.