Fig. 10.

Schematic diagram of the proposed action of fusaoctaxin A during wheat infection. When landing on wounded wheat tissues, most fungal spores can germinate and grow hyphae within 1 dpi, but neighboring intact wheat cells will launch basal defense responses, including callose deposition, chloroplast responses, and plasmodesmata closure, therefore hyphal growth can be temporarily hindered a. Later, wild-type F. graminearum hyphae can activate fg3_54 cluster expression and produce fusaoctaxin A (FA). FA can be diffused into neighboring cells, cause transcriptional changes, host defense suppression and plasmodesmata reopening, which allows fungal hyphae to penetrate cell wall and enter cell-to-cell invasion mode b; the strains lacking fg3_54 (mutant F. graminearum or non-wheat pathogen Fusarium species) cannot produce FA, and the host defenses accumulate to a stronger degree, and subsequently block fungal growth c. With exogenous application, FA can inhibit wheat defense responses and then enable hyphal cell-to-cell invasion in wheat d. Transmission electron microscopic images are shown in the bottom. PCW plant cell wall, P: papillae-like cell wall deposition, H: F. graminearum hyphae. Scale bar represent 1 μm