The emerging role of septins in fungal pathogenesis

Abstract

Fungal pathogens undergo specific morphogenetic transitions in order to breach the outer surfaces of plants and invade the underlying host tissue. The ability to change cell shape and switch between non‐polarised and polarised growth habits is therefore critical to the lifestyle of plant pathogens. Infection‐related development involves remodelling of the cytoskeleton, plasma membrane and cell wall at specific points during fungal pathogenesis. Septin GTPases are components of the cytoskeleton that play pivotal roles in actin remodelling, micron‐scale plasma membrane curvature sensing and cell polarity. Septin assemblages, such as rings, collars and gauzes, are known to have important roles in cell shape changes and are implicated in formation of specialised infection structures to enter plant cells. Here, we review and compare the reported functions of septins of plant pathogenic fungi, with a special focus on invasive growth. Finally, we discuss septins as potential targets for broad‐spectrum antifungal plant protection strategies.

The Septin Gene StSep4 Contributes to the Pathogenicity of Setosphaeria turcica by Regulating the Morphology, Cell Wall Integrity, and Pathogenic Factor Biosynthesis

“…The observed abnormal appressorium enlargement, malformation of mycelia, and altered chitin distribution in Δ StSep4 knockout mutants likely reflect the absence of StSep4 from the key protein complexes. Septins typically act as part of a protein complex, forming a scaffold for accumulation of proteins involved in cell wall maintenance and acting a membrane diffusion barrier in mycelia . Deletion of a given septin would therefore interfere with the ability of substances to accumulate in their appropriate positions within mycelial cells, altering the polar growth of the mycelium.…”

“…Septins typically act as part of a protein complex, forming a scaffold for accumulation of proteins involved in cell wall maintenance and acting a membrane diffusion barrier in mycelia. 42 Deletion of a given septin would therefore interfere with the ability of substances to accumulate in their appropriate positions within mycelial cells, altering the polar growth of the mycelium. Given the role of septin-based complexes in recruiting and scaffolding chitin synthase, absence of StSep4 may also have impaired the assembly of chitin with other cell wall components at the hyphal tip.…”

Septin-dependent invasive growth by the rice blast fungus Magnaporthe oryzae

“…1 A). This acts to recruit a F-actin network to the appressorium base, re-modelling the cytoskeleton to facilitate re-polarisation of the infection cell (Dulal et al 2020 ; Dagdas et al 2012 ; Eisermann et al 2023 ). Both, septin and F-actin ring assembly requires the regulated generation of ROS via an NADPH oxidase complex (Egan et al 2007 ; Ryder et al 2013 ).…”

“…M. oryzae possesses six septins of which the four septin genes SEP3 , SEP4 , SEP5 and SEP6 are homologs of the S. cerevisiae core spetin genes CDC3 , CDC10 , CDC11 and CDC12 which are involved in cytokinesis (Dagdas et al 2012 ). The two non-core septins SEP7 and SEP8 belong to the class 5 group of septins, which is absent in humans and yeasts and found predominantly in filamentous fungi (Shuman and Momany 2022 ; Eisermann et al 2023 ). During the early stages of infection, the four core septins Sep3, Sep4, Sep5 and Sep6 form a large hetero-oligomeric disc- and later a ring-structure at the base of the appressorium surrounding the penetration pore (see Fig.…”