RT Journal Article SR Electronic T1 Rgs1 is a regulator of effector gene expression during plant infection by the rice blast fungus Magnaporthe oryzae JF bioRxiv FD Cold Spring Harbor Laboratory SP 2022.09.04.506535 DO 10.1101/2022.09.04.506535 A1 Tang, Bozeng A1 Yan, Xia A1 Ryder, Lauren S. A1 Cruz-Mireles, Neftaly A1 Soanes, Darren M. A1 Molinari, Camilla A1 Foster, Andrew J. A1 Talbot, Nicholas J. YR 2022 UL http://biorxiv.org/content/early/2022/09/05/2022.09.04.506535.1.abstract AB 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 selection of mutants that show constitutive effector gene expression. Using this simple screen, we identify Rgs1, a regulator of G-protein signalling (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 expression of at least 60 temporally co-regulated effector genes, preventing their transcription during the pre-penetration stage of development prior to plant infection. A regulator of appressorium morphogenesis is therefore also required for orchestration of pathogen gene expression required for invasive growth by M. oryzae during plant infection.Competing Interest StatementThe authors have declared no competing interest.