Rhizophagus irregularis gene regulation in response to rice root exudates

Purpose: The recent publication of the fungal mutualist R. irregularis genome facilitated transcriptomic studies. We here adress the gene regulation of R. irregularis in response to root exudates from rice wild-type and osnope1 (no perception candidate - mutant unable to host arbuscular mycorrhizal fungi) Methods: Spores of R. irregularis were treated with root exudates and collected at 1 hour, 24 hours and 7 days after addition. To monitor fungal gene regulation, control conditions were also prepared at T0, 1h, 24h and 7d. mRNA were sequenced by HiSeq Illumina. Reads were mapped on the Rhizophagus irregularis genome assembly (Gloin1 - Tisserant et al., PNAS, 2013) using CLCworkbench suite. Results: -At 1h, a set of 92 fungal genes were found up-regulated in response to wt root exudates (92), not to osnope1 root exudates, many of them being involved in cell signaling. -At 24h and 7d, numerous genes putatively involved in primary metabolism were up-regulated in response to wt root exudates, not in response to osnope1 root exudates -Several vital genes involved in cell development are repressed in response to osnope1 RE compared to wt RE. Conclusions: these results argue for a high metabolic activity induced by wt root exudates, not by osnope1 root exudates. mRNA sequences from spores treated with root exudates were generated by Illumina Hiseq 2000 (triplicate).