Mitogen-Activated Protein Kinase CsPMK1 Is Essential for Pepper Fruit Anthracnose by Colletotrichum scovillei

Abstract

The phytopathogenic fungus Colletotrichum scovillei, belonging to the Colletotrichum acutatum species complex, causes severe anthracnose disease on several fruits, including chili pepper (Capsicum annuum). However, the molecular mechanisms underlying the development and pathogenicity of Colletotrichum scovillei are unclear. The conserved Fus3/Kss1-related MAPK regulates fungal development and pathogenicity. Here, the role of CsPMK1, orthologous to Fus3/Kss1, was characterized by phenotypic comparison of a target deletion mutant (ΔCspmk1). The mycelial growth and conidiation of ΔCspmk1 were normal compared to that of the wild type. ΔCspmk1 produced morphologically abnormal conidia, which were delayed in conidial germination. Germinated conidia of ΔCspmk1 failed to develop appressoria on inductive surfaces of hydrophobic coverslips and host plants. ΔCspmk1 was completely defective in infectious growth, which may result from failure to suppress host immunity. Furthermore, ΔCspmk1 was impaired in nuclear division and lipid mobilization during appressorium formation, in response to a hydrophobic surface. CsPMK1 was found to interact with CsHOX7, a homeobox transcription factor essential for appressorium formation, via a yeast two-hybridization analysis. Taken together, these findings suggest that CsPMK1 is required for fungal development, stress adaptation, and pathogenicity of C. scovillei.

Role of the cAMP signaling pathway in the dissemination and development on pepper fruit anthracnose disease caused by Colletotrichum scovillei

“…The wild-type C. scovillei (strain KC05) and its transformants were routinely grown on V8 juice agar medium (V8A), potato dextrose agar medium (PDA), and oatmeal agar medium (OMA) ( Fu et al., 2022 ). Mycelia used for extraction of DAN and RNA were cultured in liquid complete medium (CM) and on TB3 agar medium ( Lee et al., 2021 ).…”

“…The qRT-PCR was performed using the StepOne real-time PCR system (Applied Biosystems, Foster city, CA) with two replicates in three independent experiments. The relative gene expression was calculated as 2 −ΔΔCT ( Livak and Schmittgen, 2001 ; Fu et al., 2022 ).…”

“…C. scovillei , a member of the C. acutatum species complex, is the major causal agent of fruit anthracnose in pepper ( Capsicum annuum L.) in tropical and subtropical regions ( Fu et al., 2021 ). The polycyclic pathogen C. scovillei produces massive conidia that propagate fruit anthracnose throughout the pepper growth season ( Fu et al., 2022 ). Upon recognition of host physical and chemical signals, C. scovillei conidium germinates and develops an appressorium at the tip of the germ tube ( Gao et al., 2018 ).…”

NADPH Oxidases Are Required for Appressorium-Mediated Penetration in Colletotrichum scovillei-Pepper Fruit Pathosystem

“…To observe the appressorium penetration site of C. scovillei on pepper fruit, the conidia suspensions (5 × 10 4 conidia/ml) were inoculated onto intact pepper fruits. After incubated in humid box at 25ºC for 3 days, the inoculation areas were sliced using a razor and fixed in 4% paraformaldehyde at 4ºC for 24 h (Fu et al, 2022). The samples were subsequently washed using 1× phosphate buffered saline.…”

CsPOM1, a DYRK Family Kinase, Plays Diverse Roles in Fungal Development, Virulence, and Stress Tolerance in the Anthracnose Pathogen Colletotrichum scovillei

“…Studying the mechanisms of fungal signaling systems provides information important for understanding fungal development and pathogenicity. One of the best-studied MAPK pathways is the Pmk1 MAPK pathway, which is required for appressorium formation and plant infection in many phytopathogenic fungi ( Xu and Hamer, 1996 ; Zhao et al., 2007 ; Liang et al., 2019 ; Fu et al., 2022 ). The high osmolarity glycerol (HOG) MAPK pathway is also one of the well-characterized MAPK pathways that mediate cellular adaptation to hyperosmotic stress ( Van Wuytswinkel et al., 2000 ; Tatebayashi et al., 2006 ; Wu et al., 2006 ; Hohmann, 2009 ; Duran et al., 2010 ; Saito and Posas, 2012 ).…”