P-377 - Molecular shields in biotrophic pathogenesis: Intrinsic disorder in elicitin-like oomycete effectors

Plant-pathogen coevolution is shaped by the constant arms race for dominance. Understanding its mechanisms could be the foundation for developing efficient crop protection strategies. In our work we focus on the oomycete pathogen Albugo candida and aim to understand the role of elicitin-like proteins (ELLs), known for activating plant immune responses, in the context of the molecular arms race, obligate biotrophy and the structure-function continuum. Prediction results showed prevalence of intrinsically disordered regions (IDRs) within the ELLs of A. candida. Removing those prior to infiltrating Arabidopsis thaliana led to an increased cell death response in comparison to infiltration with the full length ELLs, indicating aggravated recognition by the plant when IDRs are present. Furthermore, adding an IDR to INF1 - an elicitin from Phytophthora infestans recognized in Nicotiana benthamiana - revealed loss of cell death inducing properties upon infiltration. Hence, we suggest that IDRs can act as molecular shields decreasing recognition of conserved core domains, facilitating obligate biotrophy. Comparing elicitins from several oomycetes, adapted to different lifestyles, revealed an enrichment of IDRs in obligate biotrophic elicitins, indicating IDRs may be a biotrophy hallmark. Following up on IDRs could provide valuable insights regarding the molecular arms race as abilities like masking can have a significant impact on the infection success of pathogenic oomycetes.