Cytoplasmic Streaming in Neurospora: Disperse the Plug To Increase the Flow?

Michael Plamann,Susan K Dutcher

doi:10.1371/journal.pgen.1000526

Abstract

Filamentous fungi grow as extending and branching tubular cells (hyphae) that generate radially symmetric colonies. As colonies expand, hyphal tips at the periphery avoid each other to allow maximum coverage of the medium, while hyphal tips at the colony center actively fuse to generate an interconnected network of hyphae that allows the bulk movement of cytoplasm toward the colony edge [1]. Hyphal growth is a wonderful adaptation for efficient penetration and acquisition of nutrients from live or dead organisms, especially plants. Unlike multicellular eukaryotes that exist as collections of distinct cells, the syncytial mode of growth places filamentous fungi at serious risk of “bleeding” to death if there is a break in the cell wall. To avoid this fate, fungal hyphae have cross-walls or septa that are perforated to allow the flow of cytoplasm, but can be plugged in response to cellular wounding [2]–[4]. The septal “plug” used by filamentous ascomycete fungi is known as the Woronin body, and it is typically tethered to the rim of the septal pore [4]–[8].

Highlights

Filamentous fungi grow as extending and branching tubular cells that generate radially symmetric colonies
In this issue of PLoS Genetics, Seng Kah Ng et al describe a curious modification of the tethering mechanism for the Woronin body in N. crassa [10]
Ng et al describe the identification of leashin, a fungal-specific gene that encodes an organellar tether for Woronin body inheritance and cell cortex association

Summary

Introduction

Filamentous fungi grow as extending and branching tubular cells (hyphae) that generate radially symmetric colonies. In the filamentous fungus Neurospora crassa, cytoplasmic streaming can occur at incredible rates, up to 60 mm/sec [9]. The typical ‘‘trap-door’’ arrangement of the Woronin body seen in most ascomycetes might be expected to impede rapid flow of large organelles such as nuclei through septa.

Results

Conclusion