Interaction of Pathogenic Fungi with Host Cells: Molecular and Cellular Approaches
摘要
Interactions between plants and fungi are likely one of the most dynamic arms races in nature where host plants are motivated to evolve immune strategies while fungal pathogens are motivated to evolve ways to evade recognition. Recent studies have revealed that interacting processes, involving autophagy, immunity signaling pathways, and microtubule dynamics, together determine plant defenses responses. Autophagy, a conserved intracellular degradation pathway, is required for fungal pathogenicity in Magnaporthe oryzae, Fusarium graminearum, and Phytophthora sojae, as mutants disrupting autophagy-related genes lose ability to create conidia, form appressoria, and are compromised virulently. On the other side, immunity in plants is mediated by pattern-triggered immunity (PTI) pathway and effector-triggered immunity (ETI) pathway that, although in earlier research and thought antagonistic, can now be characterized as highly interconnected. Further complexity occurs when signaling interactions between PTI and ETI are investigated. These interactions occur through shared signaling components (i.e., BIK1, NADPH oxidase RbohD, and mitogen-activated protein kinases) required for management of cellular marks of PTI and ETI, such as reactive oxygen species (ROS) and induction of defense genes. The cytoskeleton is of utmost importance in this immune network as it is both a sensor and executor of signaling. Actin filaments and microtubules control Ca2+ fluxes, the function of receptor–kinase complexes, and all downstream transcriptional responses. Cytoskeletal dynamics disruption decreases not only ROS accumulation but also the hypersensitive response (HR) via changes to SG and PR (pathogenesis-related) gene expression. ADF4, BIK1, and BAK1 proteins also incorporate cytoskeletal turnover with immune signaling, showing the close relationship between cell architecture and defense direction. Together, the work discussed emphasizes the role of the cytoskeleton and autophagy as major regulators of plant immunity, unveiling new insights into how plants sense, integrate, and respond to attacks from fungi. Moreover, the advances in understanding these mechanisms will present an opportunity to engineer crops for improved resistance to these devastating fungal infections.