Co-Expression Network Analysis Suggests PacC Transcriptional Factor Involved in Botryosphaeria dothidea Pathogenicity in Chinese Hickory

<i>Botryosphaeria dothidea</i> is the causative agent of Chinese hickory trunk canker, which poses significant threat to the production of Chinese hickory (<i>Carya cathayensis</i> Sarg.). Previous studies reported that endophytic-pathogenic phase transition, also referred to as latent infection, plays an important role in the interaction of <i>Botryosphaeria dothidea</i> with various host plants, including Chinese hickory. However, the mechanism underlying this phase transition is not well understood. Here, we employed RNA-Seq to investigate transcriptional changes in <i>B. dothidea</i> during its phase transition upon interaction with Chinese hickory. A co-expression network was generated based on 6391 differentially expressed genes (DEGs) identified from different infection stages and temperature treatments. One co-expressed module was found that highly correlated with temperature treatments which simulated conditions of <i>B. dothidea</i> latent infection in the field. Subsequently, 53 hub genes were detected, and gene ontology (GO) enrichment analysis revealed three categories of enriched GO terms: transmembrane transport or activity, ion homeostasis or transport, and carbohydrate metabolism. One PacC transcriptional factor (BDLA_00001555, an ambient pH regulator), and one endo-β-1,3-glucanase (BDLA_00010249) were specifically upregulated under temperature treatments that corresponded with the activation stage of <i>B. dothidea</i>'s pathogenic state. The knockout mutant strain of BDLA_00001555 demonstrated defective capability upon the activation of the pathogenic state. This confirmed that BDLA_00001555, the PacC transcriptional factor, plays an important role in the latent infection phase of <i>B. dothidea</i>. Our findings provide insights into the pathogenic mechanism of Chinese hickory trunk canker disease.