JH1327 is a transgenic line that carries an integrated "complex" array containing a PIE-1:GFP transgene, the roller marker pRF4, and digested genomic DNA. Unlike other lines carrying germline-expressed transgenes that can become silenced over time, this line has maintained robust GFP expression in the germline for over 100 generations. In the course of working with JH1327, we noticed that it consistently shows higher penetrance of phenotypes induced by RNAi (feeding method) compared to N2. For example, under conditions where nos-2(RNAi) causes only 3% sterility in N2, we observe on average 64% sterility in JH1327. Outcrossing of JH1327 to N2 showed that the RNAi hypersensitivity segregates with the complex array. To determine whether the RNAi hypersensitivity was due to the roller DNA, the PIE-1:GFP transgene or some other property specific to the array, we compared the RNAi sensitivity of JH1327 to that of 3 other transgenic strains. JR1186 is a line carrying a high copy, simple array containing pRF4 and MED-1:GFP transgenes (thanks to Morris Maduro and Joel Rothman); KK866 is a line carrying an integrated, complex array containing pRF4 and a GFP:PAR-2: fusion driven by the pie-1 promoter (thanks to Ken Kemphues); JH1461 is a line carrying an extrachromosomal, complex array containing pRF4 and a GFP:PAR-6 fusion driven by the pie-1 promoter. Like JH1327, KK866 and JH1461 show robust GFP expression in the germline that has not become silenced over time. We found that, whereas JR1186 shows the same sensitivity to RNAi as N2, KK866 and JH1461 show increased sensitivity to RNAi, in some cases as high as JH1327. These observations suggest that strains that express transgenes in the germline tend to show higher sensitivity to RNAi (at least as assayed by feeding) compared to wild-type and other transgenic strains. We are currently testing this hypothesis further by comparing the RNAi sensitivity of other complex array strains and of low copy transgenic strains generated by bombardment. In addition to providing potential insights into RNA-mediated interference, lines with increased RNAi sensitivity such as JH1327 may prove useful in RNAi screens (e.g. abstract by Pellettieri et al.).