Adult males exhibit
daf-7 expression in both the ASI and the ASJ neuron pairs in the absence of P. aeruginosa. This expression pattern difference in adult C. elegans, can be observed both through the use of a
pdaf-7::gfp transcriptional reporter as well as by fluorescence in situ hybridization (FISH) that directly probes for endogenous
daf-7 mRNA. In populations of early larval animals carrying the
pdaf-7::gfp transcriptional reporter, males and hermaphrodites were indistinguishable, with fluorescence observed only in the ASI neurons. To determine the onset of
daf-7 expression in males, we imaged animals carrying the fluorescent reporter at multiple time points during development beginning in the L4 larval stage and extending into reproductive maturity. We found that
daf-7 expression remains off in the ASJ of males through the end of the last (L4) larval stage, but is switched on during young adulthood as the animals reach reproductive maturity. In addition, we examined expression of
daf-7 in the ASI neuron pair at several matched timepoints during development and observed a significant drop in the expression of
daf-7 in the ASI neurons from L4 to young adulthood (52 hr and 64.5 hr timepoints). At subsequent timepoints during adulthood, however, expression levels in the ASI neurons remained constant as expression in the ASJ neurons increased (64.5 hr and 71.5 hr timepoints).