Nitric oxide improves the tolerance of Pleurotus ostreatus to heat stress by inhibiting mitochondrial aconitase.

Pleurotus ostreatus is widely cultivated in China. However, its cultivation is strongly affected by seasonal temperature changes, especially the high temperatures of summer. Nitric oxide (NO) was previously reported to alleviate oxidative damage to mycelia by regulating trehalose. In this study, we found that NO alleviated oxidative damage to P. ostreatus mycelia by inhibiting the protein and gene expression of aconitase (ACO), and additional studies found that the overexpression and interference of Aco could affect the content of citric acid (CA). Furthermore, the addition of exogenous CA can induce alternating oxidase (aox) gene expression under heat stress, reduce the content of H2O2 in mycelium, and consequently protect the mycelia under heat stress. An additional analysis focused on the function of the aox gene in the heat stress response of mycelia. The results show that the colony diameter of the aox overexpression (OE-aox) strains was significantly larger than that of the WT strain under heat stress (32 °C). In addition, the mycelia of OE-aox strains showed significantly enhanced tolerance to H2O2. In conclusion, this study demonstrates that NO can affect CA accumulation by regulating Aco gene and protein expression and that CA can induce aox gene expression and thereby a response to heat stress. IMPORTANCE: Heat stress is one of the abiotic stresses that affect the growth and development of edible fungi. Our previous study found that exogenous NO had a protective effect on mycelia under heat stress. However, its regulatory mechanism has not been elucidated. In this study, we found that NO could alter the respiratory pathway of mycelia under heat stress by regulating Aco. The results have enhanced our understanding of NO signaling pathways in P. ostreatus.