A Downy mildew Effector Attenuates Salicylic Acid-Triggered Immunity in Arabidopsis by interacting with the host Mediator complex

MARIE-CECILE CAILLAUD; SHUTA ASAI; GANASHYAM RALLAPALLI; SOPHIE J.M. PIQUEREZ; GEORGINA FABRO; JONATHAN D. G. JONES

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2013 p. 1 - 1

lants are continually exposed to pathogen attack but usually remain healthy because they can activate defences upon perception of microbes. However, pathogens have evolved to overcome plant immunity by delivering effectors into the plant cell to attenuate defence, resulting in disease. Recent studies suggest that some effectors may manipulate host transcription, but the specific mechanisms by which such effectors promote susceptibility remain unclear. We study the oomycete downy mildew pathogen of Arabidopsis, Hyaloperonsopora arabidopsidis (Hpa), and show here that the nuclear-localized effector HaRxL44 interacts with Mediator subunit 19a (MED19a), resulting in the degradation of MED19a in proteasome-dependent manner. The Mediator complex of ~25 proteins is broadly conserved in eukaryotes and mediates the interaction between transcriptional regulators and RNA polymerase II. We found Med19a to be a positive regulator of immunity against Hpa. Expression profiling experiments reveal tra