Abstract
Chitosan is a biopolymer with a wide range of applications. The use of chitosan in clinical medicine to control infections by fungal pathogens such as Candida spp. is one of its most promising applications in view of the reduced number of antifungals available. Chitosan increases intracellular oxidative stress, then permeabilizes the plasma membrane of sensitive filamentous fungus Neurospora crassa and yeast. Transcriptomics reveals plasma membrane homeostasis and oxidative metabolism genes as key players in the response of fungi to chitosan. A lipase and a monosaccharide transporter, both inner plasma membrane proteins, and a glutathione transferase are main chitosan targets in N. crassa. Biocontrol fungi such as Pochonia chlamydosporia have a low content of polyunsaturated free fatty acids in their plasma membranes and are resistant to chitosan. Genome sequencing of P. chlamydosporia reveals a wide gene machinery to degrade and assimilate chitosan. Chitosan increases P. chlamydosporia sporulation and enhances parasitism of plant parasitic nematodes by the fungus. Omics studies allow understanding the mode of action of chitosan and help its development as an antifungal and gene modulator.
Highlights
Chitin is a key structural component of the exoskeleton of invertebrates and fungal cell walls.Its deacetylated form, chitosan, a polycation, permeabilizes the fungal membrane in an energy-dependent manner [1]
Chitosan modulates gene expression and activates fungus development and expression of biocontrol fungi (BCF) pathogenicity factors such as serine proteases involved in the degradation of host barriers
Previous studies demonstrate the determinant role of specific genes related with oxidative stress metabolism and with plasma membrane homeostasis in the response of N. crassa to chitosan
Summary
Chitin is a key structural component of the exoskeleton of invertebrates and fungal cell walls. Chitosan gene targets have been studied using two model fungi: bakers yeast (Saccharomyces cerevisiae) and the filamentous fungus Neurospora crassa. In both organisms, reactive oxygen species (ROS) and plasma membrane seem to be key players in the mode of action of chitosan. The use of omics-derived technologies has a large potential to discover gene targets of chitosan in fungal pathogens. This could be a fundamental step to develop chitosan as an antifungal. Fungi 2016, 2, 11 chitosan could help to modulate gene functions of beneficial microbes, such as BCF This might improve their plant growth promotion and biocontrol capabilities. In this special issue contribution, we will revise molecular, cell and agronomical approaches together with omics techniques to fully understand the multimodal action of chitosan in agrobiotechnological and health applications
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