These findings establish Hip1 as a closely related homolog of PEIE1 and suggest that these closely related Alt a1-like proteins possess dual activities: modulation of HIR-associated immune signaling and activation of EDS1-dependent host cell death.
Abstract
Necrotrophic fungi secrete numerous Cell Death-Inducing Proteins (CDIPs) that manipulate host immunity to promote disease, yet the signaling pathways underlying their phytotoxic activity remain poorly understood. Here, we identify the Botrytis cinerea Hypersensitive response-inducing protein 1 (Hip1) as a close homolog of the recently described Sclerotinia sclerotiorum effector Plant Early Immunosuppressive Effector 1 (PEIE1) and investigate the molecular basis of its activity. HIP1 and PEIE1 share high sequence similarity and a conserved AlphaFold-predicted Alt a1-like fold, they interact with the Arabidopsis plasma membrane protein HIR4, and they induce strong necrosis in Nicotiana benthamiana. Despite their high structural similarity, Hip1 and PEIE1 differ in their reported roles during fungal infection. Unexpectedly, Hip1-induced cell death requires the central immune regulator ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1) as well as the downstream helper NLR network comprising ADR1 and NRG1. Together, our findings establish Hip1 as a closely related homolog of PEIE1 and suggest that these closely related Alt a1-like proteins possess dual activities: modulation of HIR-associated immune signaling and activation of EDS1-dependent host cell death.
Rice (Oryza sativa) is highly susceptible to a variety of devastating fungal diseases. However, whether these phylogenetically distinct fungal pathogens employ conserved effectors to disrupt common immune hubs remains unclear. Here, we identify a conserved virulence strategy in which multiple rice-infecting fungal pathogens employ a subtilisin-like protease effector, SBT1, to suppress host immunity. Upon secretion into plant cells, SBT1 directly targets the key immune signaling component OsMAPKKKα and mediates its degradation in a proteolytic activity-dependent manner. OsMAPKKKα acts in a linear signaling cascade: it is phosphorylated and stabilized by OsRLCK185 at Thr493, and subsequently phosphorylates OsMKK4 to activate downstream MAPK signaling. By degrading OsMAPKKKα, SBT1 disrupts the chitin-triggered immune signaling transduced through the OsCERK1–OsRLCK185–OsMAPKKKα–OsMKK4 module. Importantly, host-induced gene silencing (HIGS) targeting SBT1 confers broad-spectrum resistance against multiple fungal pathogens. Our study unveils a previously unexplored pathogen strategy wherein a secreted effector protease dismantles a central signaling node, and identifies OsMAPKKKα as a promising target for engineering disease-resistant crops.
Yuan Fang, Zhaoyun Wang, Wenjing Li et al.· Science Advances· 0 citations
It is demonstrated that the TaLYK5-TaDSK2a module functions as a molecular switch that dynamically regulates the trade-off between plant immunity and growth.
Yu Wu, Dan Yang, Haibin Zhao et al.· Proceedings of the National...· 0 citations
A previously unrecognized mechanism regulating RNase activity in a dicot PM RALPH effector is revealed and new insights are provided into the functional diversification of RALPHs and their adaptation to obligate biotrophy.
Root‐knot nematodes (Meloidogyne spp.) secrete effectors that suppress plant immunity; however, the mechanisms by which they counteract specific defense enzymes, such as chitinases, remain unclear. In this study, we demonstrate that the Meloidogyne incognita effector Minc10750 directly targets the catalytic domain of plant chitinases (Chi), serving as a critical determinant of virulence. The expression of Minc10750 is upregulated in the subventral esophageal glands during early infection. Its binding to the glycosyl hydrolase 19 domain of chitinases is strictly dependent on effector N‐glycosylation. A mutation at the asparagine glycosylation site (Minc10750‐Mu3) abolishes this modification, impairs its nuclear accumulation, and disrupts the interaction. Mechanistically, Minc10750 promotes the proteasome‐dependent destabilization of Chi proteins, thereby suppressing Chi‐triggered immunity, including mitogen‑activated protein kinase (MAPK) activation and reactive oxygen species burst. Consistently, Chi mutants exhibit enhanced susceptibility to nematodes, whereas Chi overexpression confers resistance. Transcriptome analysis further reveals that the Chi‐mediated expression of defense‐related transcription factors is compromised in Minc10750 transgenic plants. Our findings elucidate a mechanism by which a glycosylated nematode effector disables a core component of basal immunity, thereby providing a potential target for the engineering of nematode‐resistant crops.
Rui Liu, D. U. Nilunda Madhusanka, Jingjing Zhou et al.· New Phytologist· 0 citations
ABSTRACT Plant fungal pathogens secrete a plethora of effectors into host cells to facilitate their infection by interfering with the normal physiological processes of the host plant. However, the role of guanyl‐specific ribonuclease T1 effector protein in the virulence of fungal pathogens remains largely unexplored. Here, we show that an effector protein EC19, secreted by the soil‐borne fungus Fusarium oxysporum f. sp. lycopersici (Fol) that causes tomato wilt disease, contributes to the full virulence of Fol. In‐locus knockout of EC19 significantly reduced the virulence of Fol, while complementing EC19 in the knockout mutant restored the pathogenicity of Fol on tomato. EC19, which contains the ribonuclease T1‐like domain, is highly conserved across fungal species and exhibited the ability to cleave single‐stranded RNA isolated from tomato. EC19 was specifically induced during Fol infection. The AlphaFold3‐predicted structure of EC19 shows a high degree of structural similarity with ribonuclease T1 from Aspergillus oryzae, with limited similarity to RNase T2. Using Agrobacterium‐mediated transient assay in the leaves of Nicotiana benthamiana, we found that EC19 predominantly localised to the nucleus of plant cells. Stable transgenic susceptible tomato plants overexpressing EC19 exhibited increased susceptibility to Fol infection compared to wild‐type plants. RNA‐seq analysis of EC19‐overexpressing tomato lines revealed that downregulated differentially expressed genes were predominantly enriched in plant hormone signal transduction, phenylpropanoid biosynthesis, and plant–pathogen interaction pathways. Taken together, these findings indicate that EC19 with ribonuclease activity promotes Fol infection, expanding our understanding of the molecular mechanisms underlying Fol virulence.
Min Li, Yi-Fei Wang, Haoqian Li et al.· Molecular plant pathology· 0 citations
Plasmodesmata (PD) play vital roles in plant growth and defense through controlling symplastic transport of important molecules. Here we report that a conserved COBRA-like protein, COBL3, is required for PD-mediated antiviral defense (PMAD) against divergent plant RNA viruses in wheat (Triticum aestivum) and tobacco (Nicotiana benthamiana) via positively regulating callose accumulation. The wheat COBL3 protein, TaCOBL3, interacts with the 17K movement protein (MP) of barley yellow dwarf virus-GAV (BYDV-GAV). TaCOBL3 is associated with the plasma membrane and co-locates with 17K MP at PD. Genetic analysis with overexpression and knockout lines reveals that TaCOBL3 positively regulates wheat defense against BYDV-GAV through modulating callose accumulation at PD. Interestingly, TaCOBL3 interacts with the wheat homolog of PDLP5, a conserved key PD permeability regulator in higher plants. Silencing TaPDLP5 diminishes the elevated BYDV-GAV defense conferred by TaCOBL3 overexpression in wheat. Furthermore, transient expression of TaCOBL3 promotes callose accumulation and lowers PD permeability in tobacco cells, which is, however, largely compromised when tobacco PDLP5 is silenced. Notably, BYDV 17K MP weakens the interaction between TaCOBL3 and TaPDLP5 and inhibits their callose binding activities. Finally, silencing tobacco NbCOBL3 gene decreases callose content and attenuated host defense against two tobraviruses, one potexvirus, and one hordeivirus. Overall, our study reveals a previously unknown role of COBRA-like proteins in PMAD and provides insight into how a plant viral MP sabotages PMAD through perturbing COBL3-PDLP5 interaction to facilitate virus spread through PD. The conserved COBL3 gene may represent a valuable target for engineering broad-spectrum antiviral resistance in crop plants.
Jin Yang, Kai Gao, Xiaohuan Jin et al.· Plant Communications· 0 citations
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