Biology subjects

Molinari, C.

Publications and source records attributed to Molinari, C..

4 recordsLinked to original sources

bioRxiv2026

A Pmk1-Regulated Mst12-Bip1 Network Coordinates Appressorium Function, Effector Deployment, and Invasive Growth by Magnaporthe oryzae

To cause rice blast disease, the filamentous fungus Magnaporthe oryzae develops a specialised infection cell called an appressorium, which generates enormous turgor to breach the rice leaf cuticle. Although key regulators of appressorium development have been identified, it is not known how they drive the extensive transcriptional reprogramming required for infection-related morphogenesis. Here, we show that the Pmk1 MAP kinase orchestrates plant infection by regulating a transcriptional network controlled by the Mst12 and Bip1 transcription factors. Bip1 is regulated both by Pmk1-dependent phosphorylation and at the transcriptional level, while Mst12 binds to a cis-acting element upstream of BIP1 essential for pathogenesis. Bip1 and Mst12 are both necessary for regulating a set of Pmk1-dependent appressorium-specific genes, including transcriptional regulators, cell wall-degrading enzymes, and effector proteins. In addition, Mst12 specifically regulates functions required for appressorium-mediated penetration, while Bip1 controls a distinct sub-set of effector genes deployed during invasion of plant tissue. When considered together, these findings define a Pmk1-dependent transcriptional network required for plant infection by the blast fungus.

molecular biology↗

bioRxiv2022

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

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.

molecular biology↗

bioRxiv2021

Chloroplast movement and positioning protein CHUP1 is required for focal immunity against Phytophthora infestans

Communication between cellular organelles is essential for mounting effective innate immune responses to eliminate pathogens. In plants, the transport of cellular organelles to pathogen penetration sites and their assembly around the host membrane delineating plant-pathogen interface are well-documented. However, whether organelles associate with these specialized plant-pathogen membrane interfaces and the extent to which this process contributes to immunity remain unknown. Here, we discovered defense-related membrane contact sites (MCS) comprising a membrane tethering complex between chloroplasts and the extrahaustorial membrane (EHM) surrounding the pathogen haustorium. The assembly of this membrane tethering complex relies on the association between the chloroplast outer envelope protein CHLOROPLAST UNUSUAL POSITIONING 1 (CHUP1), and its plasma membrane-associated partner, KINESIN-LIKE PROTEIN FOR ACTIN-BASED CHLOROPLAST MOVEMENT 1 (KAC1). Our biochemical assays revealed that CHUP1 and KAC1 interact, while infection cell biology demonstrated their co-accumulation in foci where chloroplasts contact the EHM. Genetic depletion of CHUP1 or KAC1 reduces the deposition of callose--a cell wall material typically deployed to fortify pathogen penetration resistance--around the haustorium, without affecting other core immune processes. Our findings suggest that the chloroplast-EHM attachment complex positively regulates plant focal immunity, revealing the key components and their potential roles in the targeted deposition of defense components at the pathogen interface. These results advance our understanding of organelle-mediated immune responses and highlight the significance of MCS in plant-pathogen interactions.

plant biology↗

bioRxiv2020

A hierarchical transcriptional network controls appressorium-mediated plant infection by the rice blast fungus Magnaporthe oryzae

Rice blast is a pervasive and devastating disease that threatens rice production across the world. In spite of its importance to global food security, however, the underlying biology of plant infection by the blast fungus Magnaporthe oryzae remains poorly understood. In particular, it is unclear how the fungus elaborates a specialised infection cell, the appressorium, in response to surface signals from the rice leaf. Here, we report the identification of a network of temporally co-regulated transcription factors that act downstream of the Pmk1 mitogen-activated protein kinase pathway to regulate gene expression during appressorium-mediated plant infection. We have functionally characterised this network of transcription factors and demonstrated the operation of a hierarchical transcriptional control system. We show that this tiered regulatory mechanism involves Pmk1-dependent phosphorylation of the Hox7 homeobox transcription factor, which represses hyphal-associated gene expression and simultaneously induces major physiological changes required for appressorium development, including cell cycle arrest, autophagic cell death, turgor generation and melanin biosynthesis. Mst12 then regulates gene functions involved in septin-dependent cytoskeletal re-organisation, polarised exocytosis and effector gene expression necessary for plant tissue invasion.

microbiology↗