Fig. 7

Hypothetical working model showing folate-mediated one-carbon metabolism is required for the parasitism of P. sedebokerense. Folate and methionine participate in the folate cycle and the methionine cycle of one-carbon metabolism, respectively. These pathways produce nucleotides, NADPH, glutathione and methyl groups, which are crucial products associated with cell proliferation, redox balancing, ROS scavenging and methylation reaction in the fungus P. sedebokerense, allowing it to successfully parasitize its algal host H. pluvialis. However, such metabolic processes were arrested by applying antifolates (this study) or inhibitors targeting methionine biosynthesis [40], resulting in restrained infections of P. sedebokerense on H. pluvialis, collectively suggesting that folate-mediated one-carbon metabolism is required for the parasitism of P. sedebokerense