An orphan protein of Fusarium graminearum modulates host immunity by mediating proteasomal degradation of TaSnRK1α

Abstract

Fusarium graminearum is a causal agent of Fusarium head blight (FHB) and a deoxynivalenol (DON) producer. In this study, OSP24 is identified as an important virulence factor in systematic characterization of the 50 orphan secreted protein (OSP) genes of F. graminearum. Although dispensable for growth and initial penetration, OSP24 is important for infectious growth in wheat rachis tissues. OSP24 is specifically expressed during pathogenesis and its transient expression suppresses BAX-or INF1-induced cell death. Osp24 is translocated into plant cells and two of its 8 cysteine-residues are required for its function. Wheat SNF1-related kinase TaSnRK1α is identified as an Osp24-interacting protein and shows to be important for FHB resistance in TaSnRK1α-overexpressing or silencing transgenic plants. Osp24 accelerates the degradation of TaSnRK1α by facilitating its association with the ubiquitin-26S proteasome. Interestingly, TaSnRK1α also interacts with TaFROG, an orphan wheat protein induced by DON. TaFROG competes against Osp24 for binding with the same region of TaSnRKα and protects it from degradation. Overexpression of TaFROG stabilizes TaSnRK1α and increases FHB resistance. Taken together, Osp24 functions as a cytoplasmic effector by competing against TaFROG for binding with TaSnRK1α, demonstrating the counteracting roles of orphan proteins of both host and fungal pathogens during their interactions.

Proteomics-Based Data Integration of Wheat Cultivars Facing Fusarium graminearum Strains Revealed a Core-Responsive Pattern Controlling Fusarium Head Blight

“…In addition, two other proteins (TraesCS1A01G350500.1 and TraesCS3A01G282800.1), respectively known as TaSnRK1α1-A and TaSnRK1α2-A, were identified to be similarly downregulated in the three cultivars facing FHB. Previously shown to be involved in F. graminearum toxin tolerance (Perochon et al, 2019), TaSnRK1α proteins are also known to be targeted by the fungal OSP24 effector in order to trigger their degradation through the SCF (Skp-Cullin-F-box) ubiquitin ligase complex and the 26S proteasome (Jiang et al, 2020). The observed abundance decrease of these two proteins could suggest a fungal manipulation of this defense process that enhances wheat susceptibility independently of the plant and fungal genetics.…”

SnRK1.1‐mediated resistance of Arabidopsis thaliana to clubroot disease is inhibited by the novel Plasmodiophora brassicae effector PBZF1

“…Recent studies have shown that SnRK1 promotes plant resistance against many plant pathogens, such as geminivirus, B. graminis f. sp. hordei, F. graminearum, and several rice pathogens (Filipe et al, 2018;Han et al, 2020;Hao et al, 2003;Jiang et al, 2020). Because SnRK1.1 is the main SnRK1 kinase in A. thaliana (Jossier et al, 2009), to determine whether SnRK1 is involved in resistance to clubroot disease, two SnRK1.1-RNA interference (RNAi) lines and two SnRK1.1-overexpression (OE) lines were inoculated with P. brassicae resting spores, and the occurrence of clubroot disease was investigated at 28-30 days postinoculation (dpi).…”

The Dis1/Stu2/XMAP215 Family Gene FgStu2 Is Involved in Vegetative Growth, Morphology, Sexual and Asexual Reproduction, Pathogenicity and DON Production of Fusarium graminearum

“…The PH-1 strain is the standard strain of F. graminearum which was completely sequenced in Cuomo et al (2007). In the recent years, PH-1 strain has become a model strain in plant pathology and fungal genetics (Liu et al, 2017;Chen et al, 2019;Jiang et al, 2020). More importantly, the genetic transformation and fluorescence labeling technologies of PH-1 are now perfect and convenient.…”