A Blast Fungus Effector Targets a Tubby-like F-box Protein to Suppress Plant Immunity

Abstract

The blast fungus Magnaporthe oryzae is one of the most destructive pathogens of rice, secreting effector proteins that reprogram host cells to enable infection. Identifying plant targets of these fungal effectors is central to understanding how blast disease is established, but the targets and mechanisms of most effectors remain unknown. Here, we show that a Zinc finger (ZiF)-family effector, Tie1, targets the rice Tubby-like protein (TLP) family, which are membrane-associated plant immunity regulators whose exact functions have not been defined. Tie1 binds a range of rice TLPs and specifically engages with the Tubby-like domain of OsTLP7. Co-expression in planta with Tie1 re-localises this domain from the plasma membrane to the cytoplasm and nucleus, a shift also observed by disrupting the OsTLP7 phosphatidylinositol 4,5-bisphosphate (PIP2)-binding site in the absence of the effector. By combining AlphaFold3 structural predictions with allelic variation, we define a putative Tie1/OsTLP7 interface distal to the PIP2-binding site. Furthermore, Tie1 induces transcriptional activation activity of the OsTLP7 Tubby-like domain, and Tie1 overexpression in stable Arabidopsis lines leads to upregulation of genes that repress jasmonic acid (JA) signalling. Taken together, our results indicate that Tie1 inhibits PIP2 binding by OsTLP7 to drive its re-localisation to the nucleus and thereby modulating transcription to suppress JA-mediated plant immunity.