eat-5 encodes a Caenorhabditis elegans innexin, a component of gap junctions between the muscle cells in the pharynx. The
eat-5 null worms grow normally on an easy-to-eat strain of E. coli, HB101, but arrest as L1s on a harder-to-eat strain, DA837, a derivative of OP50. This difference in growth on two E. coli strains makes
eat-5 a convenient co-transformation marker. This is particularly useful for situations when
rol-6 is not good because the movement phenotype is studied. The gene of interest is co-injected into the
eat-5(
ad1402) null strain DA1402 with the genomic fragment containing the
eat-5 gene, and the injected worms are transferred on the DA837 E. coli. Only transgenic F1s will grow. (It is important to use the null allele
ad1402--mutants carrying the weak allele
ad464 can grow on DA837.) Once the transgenic strains are isolated, they can be maintained on DA837, so a population of adult transgenic worms is easily obtained. If non-transgenic sibs are needed for controls, a transgenic worm can be transferred on HB101, so that non-transgenics can grow. In this case, however, a second marker, such as GFP, is needed to identify transgenics.