Transcriptome Analysis of Tall Fescue Endophyte-Infected and Endophyte-Free Tissues Under Stress Conditions

Tall fescue (Lolium arundinaceum) plants symbiotic with the endophytic fungus, Epichloe coenophiala , (E+), have been shown to have better survivability and persistence than plants lacking the endophyte (E-).  To understand more about the grass-endophyte interactions and how endophyte affects the host plant physiology and gene expression, a greenhouse time course study was conducted in which water was withheld from 0 - 5 days, and endophyte effects were investigated on plant and fungal metabolites and gene expression profiles at the two day water-withholding time point.  For gene expression analysis, an in house tall fescue transcriptome assembly was generated using the RNA-Seq reads and mapping onto the assembly was done using CLC Genomics Workbench.  Analysis of differential gene expression was done using JMP Genomics and significant differences (>4-fold; P<0.001) was calculated using computed adjustments for each contrast.  Comparison of whole transcriptome expression profiles of the control versus stressed plants revealed a large number genes differentially expressed due to the stress treatment, and is similar to what has been shown previously for number of other species.  When comparing the differentially expressed gene between the E+ and E- plants under stress conditions, a lower number of differentially expressed were observed in the E+ tissues than in the E- tissues suggesting that the presence of the endophyte may modulate the effect of the stress imposed.  Results of the pathways affected will be presented and discussed.