Integrated transcriptomic and secretomic approaches reveal critical pathogenicity factors in Pseudofabraea citricarpa inciting citrus target spot.

Target spot is a newly emerging citrus disease caused by Pseudofabraea citricarpa. Outbreaks of this disease result in massive economic losses to citrus production. Here, an integrated study involving comparative transcriptomic and secretomic analyses was conducted to determine the critical pathogenicity factors of P. citricarpa involved in the induction of citrus target spot. A total of 701 transcripts and their cognate proteins were quantified and integrated. Among these transcripts and proteins, 99 exhibited the same expression patterns. Our quantitative integrated multi-omic data highlight several potentially pivotal pathogenicity factors, including 16 unigenes that were annotated as plant cell-wall-degrading enzymes, 13 unigenes homologous to virulence factors from various fungi, and one unigene described as a small cysteine-rich secreted protein, were screened and analysed. The screening of differentially expressed genes that encode secondary metabolism core enzymes implicated terpene metabolism in the pathogenicity of P. citricarpa. Overall, results indicated that plant cell wall degradation, plant-pathogen protein/polyribonucleotide interaction, and terpene biosynthesis have critical roles in the pathogenicity of P. citricarpa. This work demonstrated that integrated omic approaches enable the identification of pathogenicity/virulence factors and provide insights into the mechanisms underlying the pathogenicity of fungi. These insights would aid the development of effective disease management strategies.