Tea-oil tree (Camellia oleifera) is an important edible oil woody plant with a planting area of over 3,800,000 hectares in southern China. Pestalotioid fungi are associated with a wide variety of plants worldwide along with endophytes, pathogens, and saprobes. In this study, symptomatic leaves of C. oleifera were collected from Guangdong, Guangxi, Hainan, Hunan, and Jiangsu Provinces and pestalotioid fungi are characterized based on combined sequence data analyses of internal transcribed spacer (ITS), beta tubulin (tub2), and translation elongation factor 1-alpha (tef-1α) coupled with morphological characteristics. As a result, seven species were confirmed, of which five species are described as new viz. N. camelliae-oleiferae, P. camelliae-oleiferae, P. hunanensis, P. nanjingensis, P.nanningensis, while the other two are reported as known species, viz., N. cubana and N. iberica. Pathogenicity assays showed that all species except for P. nanjingensis developed brown lesions on healthy leaves and P. camelliae-oleiferae showed stronger virulence.

Colletotrichum spp. is ranked in the top 10 plant fungal pathogens and serves as a model for the study of hemibiotrophic pathogens, but its molecular mechanisms of pathogenesis remain largely unknown. Among species of Colletotrichum , C. fructicola causes anthracnose disease on more than 50 plants, such as pears, apples, and the important, edible-oil plant Camellia oleifera .

The tea-oil tree (Camellia oleifera Abel.) is a commercial edible-oil tree in China, and anthracnose commonly occurs in its plantations, causing great losses annually. We have previously revealed that CfSnf1 is essential for pathogenicity in Colletotrichum fructicola, the major pathogen of anthracnose on the tea-oil tree. Here, we identified CfGcn5 as the homolog of yeast histone acetyltransferase ScGcn5, which cooperates with ScSnf1 to modify histone H3 in Saccharomyces cerevisiae. Targeted gene deletion revealed that CfGcn5 is important in fungi growth, conidiation, and responses to environmental stresses. Pathogenicity assays indicated that CfGcn5 is essential for C. fructicola virulence both in unwounded and wounded tea-oil tree leaves. Further, we found that CfGcn5 is localized to the nucleus and this specific localization is dependent on both NLS region and HAT domain. Moreover, we provided evidence showing that the nuclear localization is essential but not sufficient for the full function of CfGcn5, and the NLS, HAT, and Bromo domains were proven to be important for normal CfGcn5 functions. Taken together, our studies not only illustrate the key functions of CfGcn5 in growth, development, and pathogenicity but also highlight the relationship between its locations with functions in C. fructicola.

The tea-oil tree Camellia oleifera is native to China and is cultivated in many parts of southern China. This plant has been grown for over 2,000 years, mainly for its high-quality cooking oil. Anthracnose is the main disease of tea-oil tree and results in a huge loss annually. Colletotrichum fructicola is a major pathogen causing anthracnose on tea-oil tree. In a previous study, we characterized that the bZIP transcription factor CfHac1 controlled the development and pathogenicity of C. fructicola. Here, we identified and characterized the function of CfVAM7 gene, which was significantly downregulated at the transcriptional level in the ΔCfhac1 strain under dithiothreitol stress. Targeted gene deletion revealed that CfVam7 is important in growth, pathogenicity, and responses to endoplasmic reticulum-related stresses. Further analysis revealed that CfVam7 is required for appressorium formation and homotypic vacuole fusion, which are important for fungal pathogen invasion. Cytological examinations revealed that CfVam7 is localized to vacuole membranes in the hyphal stage. The Phox homology (PX) and SNARE domains of CfVam7 were indispensable for normal cellular localization and biological function. Taken together, our results suggested that CfVam7-mediated vacuole membrane fusion promotes growth, stress response, and pathogenicity of C. fructicola.

Tea-oil Camellia species as edible-oil producing trees are widely cultivated in southern China. Camellia anthracnose that is mainly caused by Colletotrichum fructicola is a major disease of tea-oil trees. However, rapid detection and precise quantification of C. fructicola in different Camellia species that are crucial for the fundamental study of this pathosystem and effective disease management remain largely unexplored. Here, we developed a sensitive, rapid, and accurate method for quantifying C. fructicola growth in different Camellia species using a quantitative PCR assay. Amplified C. fructicola DNA using ITS-specific primers is relatively compared with the amplification of Camellia oleifera using the TUB gene. We determined that the fungal growth is tightly associated with the disease development in Ca. oleifera following C. fructicola infection in a time-course manner. This assay is highly sensitive, as fungal growth was detected in six different inoculated tea-oil Camellia species without visible disease lesion symptoms. Additionally, this method was validated by quantifying the Camellia anthracnose in orchards that did not show any disease symptoms. This assay enables the rapid, highly sensitive, and precise detection and quantification of C. fructicola growth in different tea-oil Camellia species, which will have a practical application for early diagnosis of anthracnose disease under asymptomatic conditions in Camellia breeding and field and will facilitate the development of tea-oil trees and C. fructicola interaction as a mold system to study woody plant and fungal pathogens interaction.

Anthracnose, caused by Colletotrichum species, induces significant economic damages to crop plants annually, especially for Camellia oleifera. During infection, the counter-defence mechanisms of plant pathogens against ROS-mediated resistance, however, remain poorly understood. By employing Weighted Gene Co-expression Network Analysis (WGCNA), we identified ACTIVATOR PROTEIN-1 (AP-1), a bZIP transcription factor, as significant to infection. And deletion of CfAP1 inhibited aerial hyphae formation and growth under oxidative stress. Furthermore, RNA-seq analysis post H₂O₂ treatment revealed 33 significantly down-regulated genes in the AP-1 deficient strain, including A12032, a dual specificity phosphatase (DSP) homologous to MSG5 from Saccharomyces cerevisiae. This ΔCfmsg5 strain showed enhanced oxidative tolerance, reduced ROS scavenging, and negative regulation of the CWI MAPK cascade under oxygen stress, suggesting its involvement in oxidative signal transduction. Importantly, we provide evidence that CfMsg5 regulates growth, endoplasmic reticulum stress, and several unfolded protein response genes upregulated in ΔCfmsg5. Collectively, this study identified core components during C. fructicola infection and highlights a potential regulatory module involving CfAp1 and CfMsg5 in response to host ROS bursts. It provides new insights into fungal infection mechanisms and potential targets like CfAP1 and CfMSG5 for managing anthracnose diseases.