Diverse strategies conferring extreme cadmium (Cd) tolerance in the dark septate endophyte (DSE), Exophiala pisciphila: Evidence from RNA-seq data

Dark septate endophytes (DSE) ubiquitously colonize the roots of plants growing in extreme heavy metals (HMs)-contaminated soils. Little is known about the overall molecular response of DSE to excessive HMs. Therefore, RNA-seq was performed through Illumina Hiseq 2000 sequencing based on two cDNA libraries of the DSE strain Exophiala pisciphila, cultured under cadmium (Cd)-free and Cd-stressed conditions, and 21,376 unigenes were generated. In total, 575 differentially expressed genes (DEGs) were obtained. Approximately 40% of the DEGs (228 unigenes) were involved in 10 well-known HMs-tolerant pathways, conferring the extreme cadmium (Cd) tolerance of E. pisciphila, including metal ion binding and transportation, organic acid metabolism and transportation, reactive oxygen species (ROS) scavenging, redox homeostasis, transcription factors production, sulfate assimilation, DNA repair and cell wall integrity maintenance, etc. Our results indicate that integral tactics associated with the collaboration of extracellular and intracellular mechanisms contribute to the enhanced HMs tolerance of this fungus. This study represents the first investigation of the transcriptome of DSE under Cd stress, and our results provide valuable information for future molecular studies of HMs tolerance in fungi.