A Hyaloperonospora arabidopsidis (Hpa) effector that alters plant development and increases susceptibility to pathogens interacts with BIM1, an Arabidopsis transcription factor involved in Brassinosteroids signaling

FABRO GEORGINA; BOGINO MARIA FLORENCIA

Salta

Congreso; Joint LV Annual meeting of the Society for Biochemistry and Molecular Biology (SAIB) and XIV PABMB Congress; 2019

SAIB

HaRxL106 is an effector from Hyaloperonospora arabidopsidis (Hpa), an obligated biotrophic oomycete pathogen of the plant Arabidopsis thaliana. It has a modular structure, with an N-terminal RxLR domain that is probably implied in its translocation to the host cytosol and a C- terminal domain through which this effector interacts with several host proteins.Preliminar data of Yeast-two-Hybrid studies (Y2H) indicated HaRxL106 interaction with BIM1, a member of a small family of bHLH transcription factors. After brassinosteoid signal perception BIM1 heterodimerizes with BES1 activating many BR-responsive genes. We here confirmed the HaRxL106-BIM1 interaction in planta, by co-expressing both full-length proteins fused to either the N-terminal domain of YFP (YFPn-HaRxL106) or the C-terminal of CFP (BIM1-CPFc) and performing BiFC assays in N. benthamiana. Additionally, we developed Co-IP assays in the same plant using the YFP-HaRxL106 and BIM1-FLAG constructs. On the other hand, when HaRxL106 is constitutively expressed in planta, the transgenics phenocopy the Shade Avoidance Syndrome (SAS), and those plants are more susceptible to biotrophic and hemibiotrofic pathogens. Therefore, we are interested in elucidating if those phenotypes are dependent on BIM1. Pseudomonas syringae pv. tomato (Pst DC3000) and Hpa (isolate Noco2) infection assays in bim123 knockout lines showed that these plants are more disease resistant compared to wild type (ecotype Col0), as we observed less bacterial growth, and reduced conidiophore production. Interestingly, bim123 plants produced less callose deposition when infiltrated with Pst DC3000, and showed reduced expression of the defense-gene marker PR1 after 24 hpi compared to control plants. Our results suggest that BIM1 could be a susceptibility factor for Hpa, being modulated by the HaRxL106 effector. To assess this, we continue investigating susceptibility phenotypes in bim123 plants transformed with HaRxL106 under the control of constitutive or inducible promoters.