Septins Focus Cellular Growth for Host Infection by Pathogenic Fungi.

Michelle Momany,Nicholas J Talbot

doi:10.3389/fcell.2017.00033

Abstract

One of the key challenges faced by microbial pathogens is invasion of host tissue. Fungal pathogens adopt a number of distinct strategies to overcome host cell defenses, including the development of specialized infection structures, the secretion of proteins that manipulate host responses or cellular organization, and the ability to facilitate their own uptake by phagocytic mechanisms. Key to many of these adaptations is the considerable morphogenetic plasticity displayed by pathogenic species. Fungal pathogens can, for example, shift their growth habit between non-polarized spores, or yeast-like cells, and highly polarized hyphal filaments. These polarized filaments can then elaborate differentiated cells, specialized to breach host barriers. Septins play fundamental roles in the ability of diverse fungi to undergo shape changes and organize the F-actin cytoskeleton to facilitate invasive growth. As a consequence, septins are increasingly implicated in fungal pathogenesis, with many septin mutants displaying impairment in their ability to cause diseases of both plants and animals. In this mini-review, we show that a common feature of septin mutants is the emergence of extra polar outgrowths during morphological transitions, such as emergence of germ tubes from conidia or branches from hyphae. We propose that because septins detect and stabilize membrane curvature, they prevent extra polar outgrowths and thereby focus fungal invasive force, allowing substrate invasion.

Highlights

Fungi are responsible for many of the world’s most serious diseases, ranging from crop diseases— which each year severely restrict the global harvest of many of our most important food sources—to human diseases that claim many hundreds of thousands of lives annually (Brown et al, 2012; Fisher et al, 2016)
One of the most basic features of fungal pathogens is their ability to undergo shape changes, in order to traverse the outer barriers to infection, and gain entry to underlying tissue, which they can invade and colonize with great efficiency
We recognize that septins play critical roles in cytokinesis, cell cycle control, spatial compartmentalization, and as ER and plasma membrane diffusion barriers. Though these roles are undoubtedly important for fungal growth and pathogenesis, they have been extensively reviewed elsewhere (Joo et al, 2005; Gladfelter, 2006, 2010; Lindsey and Momany, 2006; Lichius et al, 2011; Hernandez-Rodriguez and Momany, 2012; Mostowy and Cossart, 2012; Spiliotis and Gladfelter, 2012; Bridges and Gladfelter, 2014). In this mini-review, we focus instead on the role of septins in the morphogenetic switch from non-polar to polar growth, generally seen in filamentous fungi as the formation of polar outgrowths, and the importance of this switch for tissue invasion and fungal pathogenesis

Summary

Septins Focus Cellular Growth for Host Infection by Pathogenic Fungi

Reviewed by: Qing-Ming Qin, Jilin University, China James Bernard Konopka, Stony Brook University, USA. For example, shift their growth habit between non-polarized spores, or yeast-like cells, and highly polarized hyphal filaments. These polarized filaments can elaborate differentiated cells, specialized to breach host barriers. Septins are increasingly implicated in fungal pathogenesis, with many septin mutants displaying impairment in their ability to cause diseases of both plants and animals. In this mini-review, we show that a common feature of septin mutants is the emergence of extra polar outgrowths during morphological transitions, such as emergence of germ tubes from conidia or branches from hyphae. We propose that because septins detect and stabilize membrane curvature, they prevent extra polar outgrowths and thereby focus fungal invasive force, allowing substrate invasion

INTRODUCTION

Reduced virulence on corn

HOW DO SEPTINS FOCUS INVASIVE GROWTH BY FUNGI?