We also tested RNAi by feeding for two genes simultaneously. When we fed one embryonic lethal gene and one non-lethal gene, we found a reduced penetrance of embryonic lethality compared to feeding the lethal gene alone: feeding gpb-1 and unc-22 together reduced the embryonic lethality to 50% (versus 100% for gpb-1 alone) and feeding par-3 and unc-22 together reduced the lethality to 85% (versus 96% for par-3 alone). Furthermore, in both cases the resulting progeny also failed to display the unc-22 phenotype (data not shown). Thus, it appears that feeding two genes greatly reduces the strength of phenotype produced by either.
