Genome-wide characterization of effector proteins in Fusarium zanthoxyli and their effects on plant's innate immunity responses.

Background: Stem canker of Zanthoxylum bungeanum is a destructive forest disease, caused by Fusarium zanthoxyli, poses a serious threat to the cultivation of Z. bungeanum. The lack of research on effector proteins in F. zanthoxyli has severely limited our understanding of the molecular interactions between F. zanthoxyli and Z. bungeanum, resulting in insufficient effective control technologies for this disease.

Results: In this study, a total of 137 effector proteins (FzEPs) were predicted and characterized based on whole genome of F. zanthoxyli, with an average length of 215 amino acids, 8 cysteine residues, and a molecular weight of 23.06 kD. Besides, the phylogenetic evolution, conserved motifs, domains and annotation information of all the 137 effectors were comprehensively demonstrated. Moreover, transcriptomic analysis indicated that 24 effector genes were significantly upregulated in the early infection stages of F. zanthoxyli, which was confirmed by RT-qPCR. Following, the 24 effector DEGs were cloned and transiently over-expressed in the leaves of tobacco to evaluate their effects on the plant's innate immunity. It was found that effector proteins FzEP94 and FzEP123 induced pronounced programmed cell death (PCD), callose deposition, and reactive oxygen species (ROS) burst in tobacco leaves, whereas FzEP83 and FzEP93 significantly suppressed PCD induced by INF1, accompanied by a less pronounced callose accumulation and ROS burst.

Conclusions: In this study, we systematically characterized and functionally analyzed the effector proteins of F. zanthoxyli, successfully identifying four effector proteins that can impact the innate immune response of plants. These findings enhance our understanding of effector protein functions in F. zanthoxyli and offer valuable insights for future research on molecular interactions between F. zanthoxyli and Z. bungeanum.