Functions of the nicotinamide adenine dinucleotide phosphate oxidase family in <scp> <i>G</i> </scp> <i>anoderma lucidum</i> : an essential role in ganoderic acid biosynthesis regulation, hyphal branching, fruiting body development, and oxidative‐stress resistance

Abstract

Ganoderma lucidum has drawn worldwide interest with regard to its secondary metabolism and pharmaceutical activity. However, the development of such research has been limited because of a lack of basic biological knowledge. Nicotinamide adenine dinucleotide phosphate oxidases (Nox) have recently been highlighted because of the many important biological roles in plants and animals; however, the exact functions of Nox are still not fully understood in fungi. In this study, we identified two Nox isoforms (NoxA and NoxB) and a regulator, NoxR. RNA interference was used, and silencing of the Nox isoforms and NoxR expression indicated a central role for these genes in hyphal branching, fruiting body development, reactive oxygen species (ROS) generation, ROS resistance and ganoderic acid biosynthesis regulation. Further mechanistic investigation revealed that Nox-generated ROS elevated cytosolic Ca(2+) levels by activating a plasma membrane Ca(2+) influx pathway, thereby inducing the Ca(2+) signal pathway to regulate ganoderic acid biosynthesis and hyphal branching. Importantly, our results highlight the Nox functions in signal crosstalk between ROS and Ca(2+), and these findings provide an excellent opportunity to identify the potential pathway linking ROS networks to calcium signalling in fungi and suggest that plants, animals and fungi share a conserved signal-crosstalk mechanism.