exc-7 and mec-8 genetically interact in a fitness assay.

An average of 10 L1 worms were grown in bacteria expressing dsRNA for 5 days with GFP used as a non-targeting control. The resulting population sizes were counted using a COPAS worm sorter, and values were normalized to the GFP control and used as a proxy for fitness as previously described [102,103]. (A) A multiplicative model was used to calculate the expected fitness value for each mutant/RNAi condition, and exc-7 mutant worms subjected to mec-8 RNAi exhibit a more severe fitness defect than expected (student’s t-test). A log fitness score of 0 implies no interaction, and a negative log score implies a negative interaction. (B) Time-of-flight (TOF) and extinction (EXT) values of worm populations were also measured using the worm sorter. Lower TOF and EXT values for exc-7 mutant worms under mec-8 RNAi condition suggest a growth defect more severe than that observed in worms with loss of either exc-7 or mec-8 alone.