Metagenomic analysis of pathogenicity of puccinia xanthii on invasive plant xanthium italicum

Biological invasion refers to the establishment and proliferation of non-indigenous species in previously unoccupied areas, where they form wild populations. Xanthium italicum, an invasive species in Xinjiang, China, negatively affects local ecosystems, agriculture, and animal husbandry. In this study, we investigated the pathogenicity of Puccinia xanthii on the leaves of X. italicum by exploring the morphological characteristics of the pathogenic fungi, leaf enzyme activity measurement, photosynthesis measurement, and metagenomic sequencing. This study showed that P. xanthii infects the leaves of X. italicum, significantly reducing the activities of lyase, oxidoreductase, and antioxidant enzymes, including phenylalanine ammonia-lyase (PAL), superoxide dismutase (SOD), polyphenol oxidase (PPO), and catalase (CAT), as well as impairing photosynthesis. Furthermore, metagenomic analysis indicated that P. xanthii infection reduced the homogeneity and richness of phyllosphere microorganisms and increased the abundance of P. xanthii in the phyllosphere. Functional analysis also revealed that P. xanthii infection altered the diversity of microbial functions and eventually led to the development of disease symptoms and the demise of leaves through activated oxidative phosphorylation.