Ustilago maydis effector Jsi1 interacts with Topless corepressor, hijacking plant JA/ET signaling

• Ustilago maydis (U. maydis) is the causal agent of maize smut disease. During the colonization process, the fungus secretes effector proteins which suppress immune responses and redirect the host metabolism in favor of the pathogen. As effectors play a critical role during plant colonization, their identification and functional characterization is essential to understanding biotrophy and disease. • Using biochemical, molecular, and transcriptomic techniques, we performed a functional characterization of the U. maydis effector Jasmonate/Ethylene signaling inducer 1 (Jsi1). • Jsi1 interacts with several members of the plant co-repressor family Topless/Topless related (TPL/TPR). Jsi1 expression in Zea mays (Z. mays) and Arabidopsis thaliana (A. thaliana) leads to transcriptional induction of the ethylene response factor (ERF) branch of the jasmonate/ethylene (JA/ET) signaling pathway. In A. thaliana, activation of the ERF-branch leads to biotrophic susceptibility. Jsi1 likely activates the ERF-branch via an EAR motif, which resembles EAR motifs from plant ERF transcription factors, that interacts with TPL/TPR proteins. • EAR motif-containing effector candidates were identified from different fungal species including Magnaporthe oryzae, Sporisorium scitamineum, and Sporisorium reilianum. Interaction between plant TPL proteins and these effector candidates from biotrophic and hemibiotrophic fungi indicates the convergent evolution of effectors modulating the TPL/TPR co-repressor hub. Overall design: We analyzed two independent Arabidopsis lines expressing Jsi1 fused to mCherry (Jsi1-mCherry) under the control of the ß-estradiol (XVE) inducible promoter. As control we used an Arabidosis lines expressing mCherry under the XVE promoter. We treated lines for six hours with ß-estradiol and we took three independent replicates from each line. In addition, for the control line we also included three replicates without ß-estradiol treatment. In total we have 12 samples.