Fig. 3.

Summary. In response to external environmental stimulation, the spore germinates with the polar filament everted, forming a hollow polar tube, and then the infectious cargo is transported to inject into host cells through the polar tube. During this process, the polar tube interacts with both the microsporidian spore wall proteins and host receptors, and there are still many unknown aspects that need to be solved. PT polar tube, PF polar filament, PP polaroplast, PV posterior vacuole, Sp sporoplasm, TfR1 transferrin receptor 1