An Oomycete effector manipulates Arabidopsis Auxin and Brassinosteroid signaling pathways

BOGINO MARIA FLORENCIA; FABRO GEORGINA

Santa Fe

Congreso; XXXIII Reunión Argentina de Fisología Vegetal; 2021

Sociedad Argentina de Fisiología Vegetal

Effectors are molecules secreted by pathogens that are able to alter host defense responses and manipulate metabolic processes. HaRxL106 is an effector protein from Hyaloperonospora arabidopsidis (Hpa), an obligated biotrophic oomycete pathogen of the plant Arabidopsis thaliana. When HaRxL106 is constitutively expressed in planta (Col-0/35S:YFP-106 lines), plants become more susceptible to Hpa and to Pseudomonas syringae (Pst) and phenocopy the Shade Avoidance Syndrome (SAS) even though they are grown in normal light conditions. Assays in yeast (Y2H) and in planta (BiFC and CoIP) demonstrated HaRxL106 interaction with Arabidopsis proteins IAA11 and BIM1. The first is a negative regulator of Auxin-signaling, while BIM1 activates BR-responsive gene expression.We performed Hpa and Pst infection assays in iaa11 and bim1 mutants in order to asses if these proteins are necessary for the enhanced susceptibility observed in Col-0/35S:YFP-106 plants. Interestingly, bim1 mutants showed reduced bacterial and Hpa growth compared to wild type plants, while iaa11 mutants were more susceptible. To evaluate BR-, Auxin- and defense-related gene expression we performed qPCR-assays in the formerly described genotypes before and after infection with Hpa. We also expressed HaRxL106 into iaa11 and bim1 mutant backgrounds. Surprisingly, only iaa11/35S:YFP-106 plants reproduced the SAS-like phenotype. In addition, when HaRxL106 was expressed in an estradiol inducible way in wild type plants (Col0/pER8:HA-106 lines), a slight promotion of hypocotyl elongation was observed. Currently, we are developing qPCR-assays to evaluate BRs- Auxin- and defense-gene expression in Col0/pER8:HA-106 lines and generating iaa11 and bim1/pER8:HA-106 lines.