A Drosophila screen identifies a role for histone methylation in ER stress preconditioning

Stress preconditioning occurs when transient, sublethal stress events impact an organism's ability to counter future stresses. Although preconditioning effects are often noted in the literature, very little is known about the underlying mechanisms. To model preconditioning, we exposed a panel of genetically diverse Drosophila melanogaster to a sublethal heat shock and measured how well the flies survived exposure to endoplasmic reticulum (ER) stress. To identify genes with expression patterns predictive of preconditioning outcomes, we focused on the 10 DGRP strains at the extreme ends of our preconditioning screen. We compared the beneficial strains (RAL69, RAL93, RAL359, RAL387, RAL409) to the detrimental (RAL195, RAL304, RAL335, RAL737, RAL819) with and without heat shock (our preconditioning stress). To identify a standard mechanism for detrimental or beneficial preconditioning outcomes, we treated the five strains in each group as technical replicates instead of investigating each strain individually. We performed gene expression profiling analysis using data obtained from RNA-seq of 10 DGRP lines with and without heat shock. We compared the benefical group to the detrimental group for each treatment. In the final processed data, RAL409 was omited as an outlier based on PCA.