Fig. 2. Phytopathogenic invasion and infection such as nematodes, bacteria, viruses, and fungi. Nematodes migrate through the apoplast and invade the cell at the feeding site for nutrient acquisition. Nematodes also hijack cellular signaling pathways and generate plasmodesmatal (PD) biogenesis. Bacteria and viruses enter the apoplast through openings. Bacteria may colonize the apoplast and deliver mobile effectors, whereas the virion can move with the movement protein by manipulating and exploiting the PD. Unlike these, necrotrophic or biotrophic spores of filamentous pathogens germinate in the host surface, and infection hyphae grow through the intercellular spaces. Most phytopathogens directly or indirectly exploit cell-to-cell connections (the PD, apoplasts, and phloem) for movement, nutrients, or infection.
