An oomycete effector that induces shade avoidance like growth and suppresses plant defenses targets the AUX/IAA protein IAA11

Filamentous pathogens, such as oomycetes, employ multiple strategies to suppress plant immunity, one of which involves manipulating phytohormone signaling pathways. The effector HaRxL106 from Hyaloperonospora arabidopsidis (Hpa), known to induce shade avoidance syndrome (SAS)-like growth, has previously been shown to interact with brassinosteroid signaling components. Here, we investigate the role of HaRxL106 in altering auxin signaling, revealing that HaRxL106 targets the AUX/IAA protein IAA11, a key negative regulator of auxin responses. Our data suggest that HaRxL106 impedes the repressive function of IAA11, enhancing auxin signaling and promoting SAS, which concurrently suppresses plant immune responses. These findings provide insights into how pathogen effectors manipulate plant growth and immunity to facilitate infection.