Abstract

Penicillium digitatum is one of the most critical phytopathogens during the citrus postharvest period. However, the molecular mechanism of pathogenesis remains to be further explored. Purine is a multiple functional substance in organisms. To verify the role of the de novo purine biosynthesis (DNPB) pathway in P. digitatum , we investigated the third gene Pdgart , glycinamide ribonucleotide (GAR)-transferase, of this pathway in this study. The deletion mutant Δ Pdgart was generated in the principle of homologous recombination via Agrobacterium tumefaciens -mediated transformation (ATMT). The phenotypic assay indicated that the Δ Pdgart mutant displayed severe defects in hyphae growth, conidiation and germination, which can be rescued by the addition of exogenous ATP and AMP. Compared with wild-type strain N1, the ATP level of strain Δ Pdgart was detected to be sharply declined during conidial germination, and this was resulted from the damage to purine synthesis and aerobic respiration. The pathogenicity assay suggested that mutant Δ Pdgart infected citrus fruit but attenuated disease, which was owing to its reduced production of organic acids and activities of cell wall degradation enzymes. Additionally, the Δ Pdgart mutant showed altered sensitivity to stress agents and fungicides. Taken together, the present study provides insights into the essential functions of Pdgart , and paves the way for further study and novel fungicide development.