Transcriptome analysis reveals the role of nitric oxide in Pleurotus eryngii responses to Cd2+ stress.

Pleurotus eryngii is widely cultivated in China. However, our understanding of its transcriptional response to heavy metal stress and the underlying mechanism of nitric oxide (NO) in enhancing its tolerance to heavy metals is limited. In the present study, RNA-seq was used to generate large transcript sequences from P. eryngii exposed to cadmium chloride (CdCl2) and exogenous NO. A total of 45,833 unigenes were assembled from the P. eryngii transcriptome, of which 32,333 (70.54%) unigenes matched known proteins in the nr database. Transcriptional analysis revealed that putative genes encoding heat shock proteins (HSPs) and genes participating in glycerolipid metabolism and steroid biosynthesis were significantly up-regulated in P. eryngii exposed to 50 μM Cd (P < 0.05). P. eryngii mycelia exposed to extremely high levels of heavy metals showed an increase in biomass when exogenous NO was added to the culture. The collaboration of putative oxidoreductase, dehydrogenase, reductase, transferase genes and transcription factors such as "GTPase activator activity", "transcription factor complex", "ATP binding", "GTP binding", and "enzyme activator activity", which were significantly up-regulated in samples induced by exogenous NO, contributed to the enhancement of P. eryngii tolerance to extremely high levels of heavy metals. The study provides a new insight into the transcriptional response of P. eryngii to extremely high levels of heavy metals and the mechanism of NO in enhancing heavy metal tolerance.