The AP-1-like transcription factor ChAP1 balances tolerance and cell death in the response of the maize pathogen Cochliobolus heterostrophus to a plant phenolic

Salicylic acid represses VdMYB31 expression to enhance grape resistance to Colletotrichum viniferum

Grape (Vitis vinifera) production globally faces significant challenges from grape ripe rot (Colletotrichum viniferum). MYB transcription factors (TFs) play a crucial role in mediating plant responses to biotic stresses. However, their involvement in grapevine responses to ripe rot remains unclarified. This study employed bioinformatics to identify MYB TF genes within the grapevine genome and assessed their expression profiles post C. viniferum infection via transcriptome analysis. Among the 121 R2R3-MYB genes identified, VdMYB31, predominantly expressed in mature fruits, was notably downregulated in responding to C. viniferum infection. Heterologous expression of VdMYB31 in tomato (Solanum lycopersicum) fruits increased susceptibility to C. acutatum by suppressing salicylic acid (SA)-related gene expression. Silencing MYB31 in grape berries conferred resistance to C. viniferum. Additionally, exogenous SA application bolstered grape resistance to C. viniferum infection. These findings underscore the involvement of R2R3-MYB TFs in defending against C. viniferum, positioning VdMYB31 as a promising target for breeding grape varieties with improved resistance to ripe rot in viticulture.

ROS Stress and Cell Membrane Disruption are the Main Antifungal Mechanisms of 2-Phenylethanol against Botrytis cinerea

2-Phenylethanol (2-PE), a common compound found in plants and microorganisms, exhibits broad-spectrum antifungal activity. Using Botrytis cinerea, we demonstrated that 2-PE suppressed mycelium growth in vitro and in strawberry fruit and reduced natural disease without adverse effects to fruit quality. 2-PE caused structural damage to mycelia, as shown by scanning and transmission electron microscopy. From RNA sequencing analysis we found significantly upregulated genes for enzymatic and nonenzymatic reactive oxygen species (ROS) scavenging systems including sulfur metabolism and glutathione metabolism, indicating that ROS stress was induced by 2-PE. This was consistent with results from assays demonstrating an increase ROS and hydrogen peroxide levels, antioxidant enzyme activities, and malondialdehyde content in treated cells. The upregulation of ATP-binding cassette transporter genes, the downregulation of major facilitator superfamily transporters genes, and the downregulation of ergosterol biosynthesis genes indicated a severe disruption of cell membrane structure and function. This was consistent with results from assays demonstrating compromised membrane integrity and lipid peroxidation. To summarize, 2-PE exposure suppressed B. cinerea growth through ROS stress and cell membrane disruption.

Developmental Roles of the Hog1 Protein Phosphatases of the Maize Pathogen Cochliobolus heterostrophus

Protein phosphorylation cascades are universal in cell signaling. While kinome diversity allows specific phosphorylation events, relatively few phosphatases dephosphorylate key signaling proteins. Fungal mitogen activated protein kinases (MAPK), in contrast to their mammalian counterparts, often show detectable basal phosphorylation levels. Dephosphorylation, therefore, could act as a signal. In Cochliobolus heterostrophus, the Dothideomycete causing Southern corn leaf blight, ferulic acid (FA)—an abundant phenolic found in plant host cell walls—acts as a signal to rapidly dephosphorylate the stress-activated MAP kinase Hog1 (High Osmolarity Glycerol 1). In order to identify the protein phosphatases responsible, we constructed mutants in Hog1 phosphatases predicted from the genome by homology to yeast and other species. We found that Cochliobolus heterostrophus mutants lacking PtcB, a member of the PP2C family, exhibited altered growth, sporulation, and attenuated dephosphorylation in response to FA. The loss of the dual-specificity phosphatase CDC14 led to slow growth, decreased virulence, and attenuated dephosphorylation. Mutants in two predicted tyrosine phosphatase genes PTP1 and PTP2 showed normal development and virulence. Our results suggest that a network of phosphatases modulate Hog1’s dual phosphorylation levels. The mutants we constructed in this work provide a starting point to further unravel the signaling hierarchy by which exposure to FA leads to stress responses in the pathogen.