Rgs1 is a regulator of effector gene expression during plant infection by the rice blast fungus Magnaporthe oryzae

• DOI: 10.1073/pnas.2301358120
• Publication Date: 2023-03-13T19:11:16Z
• Authors: Bozeng Tang; Xia Yan; Lauren S. Ryder; Mark Jave A. Baut...; Neftaly Cruz-Mireles; Darren M. Soanes; Camilla Molinari; Andrew J. Foster; Nicholas J. Talbot
• Keywords: 580; Fungal Proteins; 570; Magnaporthe; Ascomycota; Gene Expression; Oryza; Biological Sciences; Signal Transduction; Plant Diseases

To cause rice blast disease, the filamentous fungus Magnaporthe oryzae secretes a battery of effector proteins into host plant tissue to facilitate infection. Effector-encoding genes are expressed only during plant infection and show very low expression during other developmental stages. How effector gene expression is regulated in such a precise manner during invasive growth by M. oryzae is not known. Here, we report a forward-genetic screen to identify regulators of effector gene expression, based on the selection of mutants that show constitutive effector gene expression. Using this simple screen, we identify Rgs1, a regulator of G-protein signaling (RGS) protein that is necessary for appressorium development, as a novel transcriptional regulator of effector gene expression, which acts prior to plant infection. We show that an N-terminal domain of Rgs1, possessing transactivation activity, is required for effector gene regulation and acts in an RGS-independent manner. Rgs1 controls the expression of at least 60 temporally coregulated effector genes, preventing their transcription during the prepenetration stage of development prior to plant infection. A regulator of appressorium morphogenesis is therefore also required for the orchestration of pathogen gene expression required for invasive growth by M. oryzae during plant infection.