# Distinct actomyosin–septin coordination governs conidiation and septation in Verticillium dahliae

## TL;DR

The paper reveals how actomyosin and septins work together during cell division in the fungus Verticillium dahliae, showing unique coordination during reproduction and growth.

## Contribution

The study identifies a novel apical budding process and distinct actomyosin–septin coordination during conidiation in a filamentous fungus.

## Key findings

- Septins transition from hourglass to double ring at the bud neck during apical budding.
- Disruption of septins causes defective nuclear segregation and delayed myosin II recruitment.
- Actomyosin and septins coordinate differently during conidiation versus hyphal septation.

## Abstract

Conidiation is the primary mode of reproduction in filamentous fungi and is essential for the dispersal of pathogenic species. However, the fundamental cellular mechanisms regulating conidiation in plant pathogenic fungi remain largely unexplored. Here, using Verticillium dahliae as a model, we investigated the dynamic assembly and function of the contractile actomyosin ring (CAR) and septins during conidiation through live‐cell imaging. We show that septins, visualized via VdCdc11‐GFP, first accumulate at the tip of budding hyphae during the transition from hyphal elongation to apical budding, and undergo an hourglass‐to‐double‐ring transition at the bud neck. Following mitosis, myosin II and actin assemble simultaneously into a contractile ring to drive cytokinesis. Disruption of core septin function results in defective nuclear segregation and aberrant nuclear migration during mitosis, as well as delayed recruitment of myosin II to the bud neck, indicating that septins scaffold cytokinetic machinery and coordinate nuclear division during conidiation. In contrast, during hyphal septation, myosin II, actin, and septins appear simultaneously as a diffuse cortical band, with septin organization dependent on actin. Collectively, these findings reveal distinct spatial and temporal coordination between actomyosin and septins in two cytokinetic contexts—conidiation and hyphal septation—and define apical budding as a specialized cytokinesis mode in V. dahliae. Our study broadens the understanding of fungal cytokinesis beyond yeast models to multicellular filamentous fungi.

Asexual reproduction is essential for the survival, dispersal, and pathogenicity of filamentous fungi, and yet, the cellular mechanisms that drive this process remain poorly understood. Using live‐cell imaging in the plant pathogen Verticillium dahliae, we uncovered a previously unknown form of cell division‐apical budding and showed that key cytokinetic components, including actomyosin and septins, operate in distinct ways during growth versus reproduction. These findings offer new insights into how conserved cellular components are adapted for specialized functions in multicellular fungi.