The MYB transcription factor PtoPHL3 positively regulates poplar resistance to canker disease caused by Dothiorella gregaria.

Diseases caused by pathogenic microorganisms impair plant growth, leading to reduced crop yields. While the molecular mechanisms of plant disease response are well understood in annual herbaceous species, they remain largely unknown in perennial woody plants. Here, we found that PtoPHL3, a key transcription factor in poplar's phosphorus starvation response, showed significant expression changes after treatments with salicylic acid and methyl jasmonate, and inoculation of Dothiorella gregaria Sacc (D. gregaria) which causes poplar canker disease. Overexpressing PtoPHL3 conferred increased resistance to D. gregaria in transgenic poplar, while RNA interference-mediated knockdown made the plants more sensitive to the pathogen. DNA affinity purification sequencing identified PtoPHL3-bound chromatin regions associated with disease response. Additionally, PtoPHL3 was found to bind the promoter of TGA6 and the gene body region of ERF5, upregulating their expression, which activates responses to D. gregaria, jasmonic acid and salicylic acid. These findings deepen our understanding of the pathogen response process in poplar and lay a theoretical foundation for research on disease resistance mechanisms and the breeding of disease-resistant germplasm.