Comparative transcriptomic analysis reveals novel insights into the response to Cr(VI) exposure in Cr(VI) tolerant ectomycorrhizal fungi Pisolithus sp. 1 LS-2017

This study identified, analyzed and compared the Cr(VI)-induced transcriptional changes between two Pisolithus sp. strains (Cr(VI)-tolerant strain (Pisolithus sp. 1 LS-2017) and Cr(VI)-sensitive strain (Pisolithus sp. 2 LS-2017) by de novo transcriptomic analysis. The results showed that a total of 93642 assembled unique transcripts representing 47,801 unigenes were obtained from the Pisolithus sp, of which, 22,353 (46.76%) unigenes matched known proteins in the Nr database. With 10 mg/L Cr(VI) treatment, 72 and 756 differentially expressed genes (DEGs) were found as compared with the control in the Pisolithus sp. 1 LS-2017 and Pisolithus sp. 2 LS-2017 respectively. For DEGs between control and 10 mg/L Cr(VI) treatment, nitrogen metabolism, cyanoamino acid metabolic, type I diabetes mellitus metabolism and beta-Alanine metabolism pathways were significantly enriched (p < 0.05) in Pisolithus sp. 1 LS-2017. Two nitrate reductase family genes (nidD, niiA) and one L-asparaginase family gene (yggW) were verified probably to play an important role in responsing to Cr(VI) tolerance and reduction in Pisolithus sp. 1 LS-2017 by quantitative reverse transcription-poly merase chain reaction (qRT-PCR). In Pisolithus sp. 2 LS-2017, alcC, aldA, lcf2 gene may play an important role in alleviating oxidative stress caused by Cr(VI). T up-regulated and PPO1 down-regulated under Cr(VI) stress are beneficial to spore pigmentation, formation and stability. In addition, MKP2 gene can accelerate programmed cell death of Pisolithus sp. 2 LS-2017 to response to Cr(VI).