Fig. 2. sem-5 expression in BWMs is necessary to prevent EMEs. (A) In a trIs10 I; sid-1(qt9) V; Ex(myo-3p::gfp(fRNA); myo-3p::gfp(rRNA); myo-3p::NLS::DsRed) background, BWM cells that are positive (NLS::DsRed2, white arrows) for the extra-chromosomal array directing the production of dsRNA targeting gfp do not produce Mb::YFP. Blue arrows indicate DsRed2-positive nuclei of ventral cord motoneurons. The expression of DsRed2 in these cells is from the trIs10 transgene, not the extra-chromosomal array. (B) A negative control expressing dsRNA targeting unc-115. White arrows indicate BWM cells that express NLS::dsRed2 and therefore are positive for the extra-chromosomal array. YFP expression in the BWMs is retained. (C) Expression of dsRNA targeting sem-5 in BWM results in numerous EMEs (white arrows). (D) Quantification of the EME phenotype in four lines (1-4) of unc-115(dsRNA) worms, four lines (1-4) of sem-5(dsRNA) worms and two lines (1 and 2) of egl-15(dsRNA) worms. Except for the trIs10 control, all strains are in the trIs10; sid-1(qt9)-null background. The full genotype of each strain can be found in Table S3 in the supplementary material. Red asterisks indicate statistical significance at the P<0.001 level versus the sid-1(qt9); trIs10 negative control. n>30 for all genotypes and error bars represent the s.e.m. The black asterisk indicates that one of the control lines displayed significantly more EMEs than the other three control lines. Scale bars: 50 µm.