Evasive Maneuvers: How can an oomycete effector tackle the transcriptional clues of Shade Avoidance?

BOGINO, MARÍA FLORENCIA; LAPEGNA SENZ JUAN MARCOS; KOURDOVA, LUCILLE TIHOMIROVA; ROMANOWSKI, ANDRES; LENNART WIRTHMUELLER; FABRO GEORGINA

Rosario

Congreso; Plant Biology Lectures 2024; 2024

Comité organizador de las PBL 2024

Arabidopsis’ downy mildew is caused by the oomycete pathogen Hyaloperonospora arabidopsidis (Hpa). This obligate biotroph secretes effector proteins that interfere with several metabolic and signaling pathways altering plant homeostasis and promoting infection. The Hpa effector protein HaRxL106 targets several plant growth regulators: the transcriptional controller RCD1, the Brassinosteroids-responsive transcription factor BIM1 and the Auxin repressor protein Aux/IAA11. RCD1 also interacts with BIM1 and IAA11, which suggests that HaRxL106 recruits these proteins forming a molecular complex in the plant cell nucleus. Plants expressing HaRxL106 are more susceptible to (hemi)biotroph pathogens and exhibit a Shade Avoidance-like Syndrome (SAS-like) even when cultivated in normal light conditions, being both phenotypes dependent on RCD1 and BIM1, but not on IAA11.Here we show that either Hpa infection or HaRxL106 expression in planta influence the transcriptional regulation of a subset of BR and Aux-related genes responsible for the deployment of SAS. Transactivation assays in N. benthamiana suggested that HaRxL106 affects the response of BIM1 target gene-promoters PRE5 and SAUR-AC. Moreover, transcriptomes of HaRxL106 over-expressor lines (HaRxL106-OE) and Col-0 wild type plants treated with far red light at the end of the day (EODFR), show a considerable degree of co-expressed genes. To better understand these interrelationships, we further analyzed the responsiveness of bim1 and iaa11 mutants and HaRxL106-OEs to EODFR. Our data support the hypothesis that BIM1 is a host susceptibility factor manipulated by the effector protein HaRxL106, thereby influencing the signaling pathways that promote SAS producing a negative impact on plant defense responses.