Cheng-Guo Duan

Plant immune responses rely on mitogen-activated protein kinase (MAPK) cascade that integrates pattern-triggered immunity and effector-triggered immunity. How fungal pathogens suppress this central signaling hub remains poorly understood. Here, we identify a secreted effector from phytopathogenic fungus Verticillium dahliae , VdHCE1, that is required for full virulence and directly targets host MAPK signaling. VdHCE1 interacts with the MAPK kinase MKK5 and is phosphorylated at threonine 166 in planta. Biochemical analyses demonstrated that VdHCE1 competes with MPK3 and MPK6 as a substrate of MKK5, thereby attenuating downstream MAPK activation. Consistently, VdHCE1 suppresses elicitor- and NLR-triggered immune responses, while deletion of VdHCE1 compromises fungal virulence in Arabidopsis and cotton. Genetic disruption of MKK5 restores the virulence of VdHCE1-deficient strains, establishing MKK5 as the functional target of VdHCE1. These findings reveal a strategy by which a filamentous fungal pathogen suppresses plant immunity by acting as a decoy substrate within the MAPK cascade and provide a molecular framework for engineering resistance to vascular wilt disease.

Reduction of DNA methylation has traditionally been associated with gene activation. Here, we show that DNA hypomethylation permits the binding of a transcriptional repressor, leading to gene silencing. In tomato, the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE TF SlSPL-CNR exhibits methylation-sensitive DNA binding and preferentially occupies unmethylated GTACGG motifs. During fruit ripening, DEMETER-LIKE 2 (SlDML2)-mediated DNA demethylation at the alcohol acyltransferase 1 ( SlAAT1 ) promoter allows SlSPL-CNR binding, which in turn represses SlAAT1 expression and thereby modulates the biosynthesis of ester metabolites—key components of fruit flavor. Structural analysis reveals that cytosine methylation introduces a steric clash with Gln94 in the SBP domain of SlSPL-CNR, explaining its methylation sensitivity. CRISPR knockout of SlSPL-CNR de-represses SlAAT1 and increases ester accumulation, confirming its inhibitory role. Importantly, this methylation-sensitive binding is conserved across SBP domain proteins from rice, maize, and tomato. Our findings reveal a mechanism in which DNA hypomethylation facilitates repressor recruitment, establishing a regulatory logic linking epigenetic dynamics to metabolic control in plants.

N ⁶ -methyladenosine (m ⁶ A), the most prevalent internal mRNA modification, regulates plant development and stress responses through modulating various mRNA metabolic processes and epigenetic effects. Although well studied in animals, its roles in plant–virus interactions have only recently begun to be elucidated. Multiple plant viruses carry m ⁶ A modifications on their RNAs, validated by MeRIP-seq, LC–MS/MS, and direct RNA sequencing. Viral RNAs acquire m ⁶ A through the recruitment or relocalization of host methyltransferase complexes, which is often mediated by viral proteins. Functionally, m ⁶ A can restrict infection by promoting viral RNA decay via YTH-domain readers and RNA surveillance pathways, or alternatively stabilize viral RNAs to enhance replication and systemic spread. In turn, viruses disrupt the functionality of host m ⁶ A machinery to promote infection. Moreover, viral infection reprograms host m ⁶ A homeostasis, altering methylation landscapes in immune and hormone pathways. These findings establish m ⁶ A as a dynamic epitranscriptomic switch in plant-virus interactions, with promising implications for antiviral strategies and crop improvement.

RNA-based immunity plays a central role in host defense against pathogens, with both hosts and pathogens continually evolving antagonistic strategies in their ongoing arms race. Although the presence of N6-methyl-adenosine (m⁶A) in viruses has been recognized for decades, its functional significance in plant antiviral defenses has only recently been revealed. Moreover, viral counterstrategies targeting m⁶A-mediated defenses remain largely unexplored. Here, we uncover a mutually antagonistic mechanism between m⁶A-mediated antiviral defense and a countermeasure employed by the RNA virus Cucumber mosaic virus (CMV). The deposition of m⁶A modification on CMV genomic RNAs was validated through m⁶A antibody-mediated MeRIP and nanopore-based direct RNA sequencing (DRS). During infection, plant m⁶A methyltransferases are translocated to the cytoplasm through their interaction with the viral coat protein (CP), facilitating viral m⁶A deposition. The plant EVOLUTIONARILY CONSERVED C-TERMINAL REGION 8 (ECT8) protein acts as a reader of viral m⁶A, destabilizing viral RNAs and mediating antiviral activity. Conversely, the CMV-2b protein, known as a viral suppressor of RNA silencing (VSR), antagonizes this defense by inhibiting viral m⁶A deposition. This occurs via direct interactions between 2b and the m⁶A methyltransferase components MTB and HAKAI, disrupting the methyltransferase complex's functionality. Furthermore, CMV-2b also downregulates global plant m⁶A levels, leading to the misexpression of defense-related transcripts. Collectively, our findings elucidate a previously unrecognized layer of host-virus interaction in which m⁶A modification serves as a regulatory battleground, positioning m⁶A dynamics as a new frontier in plant-virus coevolution.

Rhizosphere microbes can protect plants from phytopathogens, but the molecular mechanisms are often poorly understood. Here, we report that a rhizosphere bacterium, Bacillus amyloliquefaciens strain TG1-2 displays antimicrobial activity against various phytopathogenic fungi and oomycetes, in a process that is mediated by the NatA acetyltransferase complex in the phytopathogenic fungus Verticillium dahliae. We show that acetylation of the molecular chaperone Hsp83 by NatA facilitates the formation of a co-chaperone complex Hsp83-Sti1-Hsp70 involved in protein quality control. Dysfunction of NatA or disruption of Hsp83 acetylation results in dissociation of the co-chaperon complex, increasing protein degradation and fungal apoptosis. Notably, TG1-2 and its major antimicrobial compound surfactin induce a reduction in Hsp83 acetylation, enhancing protein degradation and fungal apoptosis. Thus, our study provides insights into the mechanisms underlying the antimicrobial action of a rhizosphere strain against phytopathogenic fungi.

The phenomenon of multiple-grain spikelets is frequently observed in gramineous crops. In the case of dual-floret spikelets, the upper fertile floret develops normally to form a single grain, while the lower sterile floret undergoes abortion. Here we elucidate the role of Double-Grain 1 (DG1), a gene encoding a homeobox-domain-containing protein, in regulating the lower floret meristem activity and double-grain spikelet trait in sorghum. A 35.7-kb paracentric inversion in the DG1 promoter region leads to increased DG1 expression, probably by reducing repressive histone modifications. This increase in DG1 expression transforms the degenerated lower floret into a fertile one. The use of the superior DG1 allele results in an increase of approximately 40.7% to 46.1% in grain number per panicle and a 10.1% to 14.3% increase in overall grain yield. Our findings shed light on the sorghum double-grain spikelet characteristic, offering valuable insights for high-yield breeding designs in cereals.