Nitric oxide as a developmental and metabolic signal in filamentous fungi

The short‐lived hydrophobic gas nitric oxide (NO) is a broadly conserved signaling molecule in all domains of life, including the ubiquitous and versatile filamentous fungi (molds). Several studies have suggested that NO plays a vast and diverse signaling role in molds. In this review, we summarize NO‐mediated signaling and the biosynthesis and degradation of NO in molds, and highlight the recent advances in understanding the NO‐mediated regulation of morphological and physiological processes throughout the fungal life cycle. In particular, we describe the role of NO in molds as a signaling molecule that modulates asexual and sexual development, the formation of infection body appressorium, and the production of secondary metabolites (SMs). In addition, we also summarize NO detoxification and protective mechanisms against nitrooxidative stress. NO signaling is initiated by binding of NO with soluble guanylyl cyclase (sGC). Upon the binding of NO, sGC catalyzes the conversion of GTP to cGMP followed by signal transduction. NO signaling affects diverse aspects of fungal development including conidiation, germination, formation of appressorium and sexual fruiting body. NO signaling is also involved, either as inducer or substrate, in fungal secondary metabolism.