Figure 1.

Chemosensory receptor expression is altered in the dauer stage. Promoter-GFP fusion genes were used to monitor expression of three chemosensory receptors, srd-1, str-2, and str-3 in adult (A, B, and C) and dauer (D, E, and F) animals. The head region is shown in a lateral view. White arrows denote ASI cell bodies. Adults express srd-1 and str-3 strongly and str-2 weakly in ASI (not detectable in B). Dauer larvae express str-2 and str-3 but not srd-1 in ASI. Yellow arrow in B denotes AWC cell body, which expresses str-2 in adults but not dauer larvae. The ASI neuron pair is bilaterally symmetric; in most panels, only one ASI is apparent, but in E the contralateral ASI neuron is visible. Each neuron extends a dendrite to the tip of the nose and a single U-shaped axon. Anterior is at left and dorsal is up. (Scale bars, 10 μM.)