Xiao-Lin Chen

Banana Fusarium wilt, caused by Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4), is a devastating disease of banana, but the molecular mechanism underlying its pathogenesis remains to be elucidated. In this study, we identified a sirtuin family protein, FocSir2, in Foc TR4. Global protein acetylation level was significantly increased in FocSIR2 knockout mutants compared with the wild type (WT), suggesting that FocSir2 is likely a deacetylase. FocSir2 was localized in the cytoplasm and was relatively highly expressed in conidia and during early infection. Deletion of FocSIR2 resulted in compact mycelial growth and a significant reduction in microconidium production, indicating a role for FocSIR2 in the asexual development of Foc TR4. The plate stress experiment indicates that FocSir2 plays important roles in cell wall integrity, osmotic stress, and pH stress responses. Notably, deletion of FocSIR2 led to greatly attenuated virulence toward banana corms and leaves, indicating that FocSir2 is essential for full virulence of Foc TR4. GO and KEGG analyses of differentially expressed genes from RNA-seq revealed enrichment in reactive oxygen species (ROS) metabolism and the TCA cycle. RT-qPCR confirmed that the expression of all eight ROS detoxification-related genes was reduced. The FocSIR2 knockout mutant was highly sensitive to H₂O₂ and exhibited an ROS burst during banana infection, indicating that FocSir2 is involved in the oxidative stress adaptation of Foc TR4 to the host. Further experiments demonstrated that deletion of FocSIR2 significantly decreased the activities of the TCA cycle key enzymes malate dehydrogenase and α-ketoglutarate dehydrogenase, as well as the content of acetyl-CoA. Yeast library screening and yeast two-hybrid assays identified three proteins, FocRlc1, FOIG_08568, and FocFstf1, that interact with FocSir2, and their acetylation levels were significantly increased in the FocSIR2 knockout mutant, indicating that these three proteins are targets of FocSir2. Collectively, this study demonstrates that the deacetylase FocSir2 plays important roles in the asexual development and environmental stress responses of the pathogen and participates in the pathogenesis of the banana Fusarium wilt pathogen by regulating oxidative stress adaptation to the host.

In plant–pathogen interaction, plants trigger reactive oxygen species (ROS) bursts to defend against pathogen invasion, while pathogens evolved antioxidant systems to scavenge ROS for infection. Our study reveals a regulatory mechanism of ROS adaptation and scavenging in the rice blast fungus Magnaporthe oryzae. We found that KatG1, a bifunctional catalase-peroxidase, acts as a ROS-responsive regulatory enzyme. During infection, the deacetylase Hos2 mediates the decrotonylation of KatG1 at K422, initiating the ROS clearance process. Decrotonylated KatG1 depolymerizes into monomers, interacts with the Hsp70 protein Ssb1, and translocates to the nucleus. Nuclear KatG1 promotes the dissociation of the Atf1-Tup1 complex, activating the expression of Atf1-mediated oxidoreductase genes and enhancing fungal infection. Moreover, we identified a small molecule, orcinol gentiobioside (OGB), that targets KatG1, inhibiting M. oryzae invasion. This study elucidates a regulatory mechanism of ROS metabolism and stress adaptation in plant fungal infections and provides a potential target for fungicide development to control rice blast disease.

Rice blast, caused by Magnaporthe oryzae, ranks among the most destructive diseases threatening global rice production [1]. This ascomycete pathogen is caused by the ascomycete fungus Magnaporthe o...

Pathogen-induced reactive oxygen species act as key signaling molecules in plant immunity, but their integration with epigenetic regulation remains unclear. Here, we identify the rice (Oryza sativa) histone deacetylase OsHDA705 as a redox sensor that coordinates immunity through oxidative post-translational modifications. Pathogen-induced reactive oxygen species oxidizes OsHDA705 at cysteine 256, blocking its deacylase activity. This oxidation promotes hyperacylation of the transcription factor OsIPA1 and histones, thereby activating defense gene expression. We further show that the catalase OsCATB functions as a redox mediator, reducing oxidized OsHDA705 to restore its deacetylase activity, thereby reestablishing the suppression of immunity. The fungal pathogen Ustilaginoidea virens hijacks this process via the secreted effector UvSE1, which physically interacts with the host catalase OsCATB to boost its reactive oxygen species–scavenging activity, thereby reducing the oxidation level of OsHDA705. Genetic disruption of the OsCATB-OsHDA705 module enhances broad-spectrum disease resistance. Our findings reveal a pathogen strategy to reprogram the host's redox-epigenetic regulation and establish reversible histone deacetylase oxidation as a molecular switch regulating immune transcription in plants.

Poly(A) tail shortening by deadenylases is a central checkpoint linking mRNA fate to eukaryotic development, yet its impact on fungal pathogenesis remains unexplored. Here, we uncover that the Pan2‐Pan3 deadenylase complex is a master regulator of infection in the rice blast fungus Magnaporthe oryzae . Pan2 and Pan3 form a catalytically active complex that localizes to P‐bodies and globally trims poly(A) tails to enforce mRNA quality control. Deletion of either or both subunits abolishes this quality‐control checkpoint, causing severe virulence loss due to arrested appressorium maturation, disrupted glycogen/lipid mobilization, and impaired autophagy. Integrating poly(A)‐seq and transcriptome profiling reveals 390 mRNAs whose poly(A) tails are ≥ 5 nt longer and whose steady‐state levels are elevated in the Δ pan2 Δ pan3 mutant; among them, ATG5 , GLS2 , and DES1 —key genes governing autophagy, ER quality control, and ROS detoxification respectively—are directly deadenylated by Pan2‐Pan3. Loss of deadenylation destabilizes these mRNAs and reduces their protein output, thereby crippling infection. Our findings establish Pan2‐Pan3 complex‐mediated deadenylation as an essential post‐transcriptional layer that orchestrates fungal virulence through stringent mRNA quality control, offering a novel target for crop protection.

Summary: Rice blast disease, caused by Magnaporthe oryzae, significantly threatens global rice yields. The Pmk1‐MAPK signaling pathway is crucial for the infection process, but the precise regulatory mechanisms of Pmk1 remain unclear. Our research reveals that sumoylation of Pmk1 is vital for its infectious function. A sumoylation site at K347 and two small ubiquitin‐related modifier (SUMO)‐interacting motifs (SIMs) in Pmk1 are highly conserved across fungi. This sumoylation, orchestrated by Smt3 and Siz1, reduces the phosphorylation of Pmk1 by tuning its interaction with Mst7. The Pmk1 sumoylation is high in hyphae and less in conidia, and it intensifies during appressorium maturation. It may act as a molecular brake to prevent excessive Pmk1 phosphorylation during appressorium formation, without affecting phosphatase Pmp1 or the localization of Pmk1. Mutations at K347 lead to hyperphosphorylation of Pmk1 and Mst12, and overexpression of appressorium‐related genes. The Δpmk1/Pmk1^K347R mutant shows deficiencies in storage utilization, turgor accumulation, and septin ring formation. Our study highlights the critical role of sumoylation dynamically balancing Pmk1 function via phosphorylation crosstalk, crucial for infection of M. oryzae, thus proposing a conserved target for antifungal strategies across fungal pathogens.