Balancing of the mitotic exit network and cell wall integrity signaling governs the development and pathogenicity in Magnaporthe oryzae.

Wanzhen Feng,Peng Liu,Ping Wang,Haowen Wu,Ziyi Yin,Xinyu Liu,Haifeng Zhang,Rui Yu,Muxing Liu,Xiaobo Zheng,Zhengguang Zhang,Chuyun Gao,Hui-Shan Guo

doi:10.1371/journal.ppat.1009080

Abstract

The fungal cell wall plays an essential role in maintaining cell morphology, transmitting external signals, controlling cell growth, and even virulence. Relaxation and irreversible stretching of the cell wall are the prerequisites of cell division and development, but they also inevitably cause cell wall stress. Both Mitotic Exit Network (MEN) and Cell Wall Integrity (CWI) are signaling pathways that govern cell division and cell stress response, respectively, how these pathways cross talk to govern and coordinate cellular growth, development, and pathogenicity remains not fully understood. We have identified MoSep1, MoDbf2, and MoMob1 as the conserved components of MEN from the rice blast fungus Magnaporthe oryzae. We have found that blocking cell division results in abnormal CWI signaling. In addition, we discovered that MoSep1 targets MoMkk1, a conserved key MAP kinase of the CWI pathway, through protein phosphorylation that promotes CWI signaling. Moreover, we provided evidence demonstrating that MoSep1-dependent MoMkk1 phosphorylation is essential for balancing cell division with CWI that maintains the dynamic stability required for virulence of the blast fungus.

Highlights

The cell wall plays a critical role in maintaining cell morphology and progression throughout the cell cycle, and its composition depends on species
H1-red fluorescent protein (RFP) and a MoMkk1-green fluorescent protein (GFP) gene fusion constructs into the wild-type strain Guy11
When stained with Calcofluor White (CFW), we found that hyphae grown in liquid culture exhibit a uniformly linear structure with one nucleus per cell

Summary

Introduction

The cell wall plays a critical role in maintaining cell morphology and progression throughout the cell cycle, and its composition depends on species. It varies in the cell types and developmental stages [1]. Cellulose and pectin are abundant in the primary cell wall that influence the cell wall porosity and extensibility during the cell cycle [2], while lignin found in the secondary cell wall protects the cell from the external stress [3]. The cell wall protects against the osmotic shock or mechanical stresses [6,7], and may induce the host’s immune response [8]. The cell wall integrity is critical to its function, including pathogenesis [9]

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Discussion

Conclusion