The arIs92 [egl-17p::cfp-lacZ] reporter is initially expressed in a graded fashion, highest in P6.p and lower in P5.p and P7.p. The expression in P5.p and P7.p disappears, and CFP-LacZ remains detectable only in P6.p and its descendants .
Consistent with previous findings (Kim and Li, 2004), we found that flp-20 is expressed in the TRNs (ALM, AVM, PLM, PVM), along with a few other neurons (ASE, LUA, and PVC).
During the early L3 stage, lin-17::GFP was expressed predominantly in P11.p and was barely detectable in P10.p. No expression was detected in P9.p. Subsequently, descendants of both P10.p and P11.p expressed lin- 17::GFP, with slightly higher levels in the P11.p descendants.
LIN-39 protein levels were not uniform among vulval precursor cells. P3.p and P4.p displayed the lowest LIN-39 levels, and the level of LIN-39 in P4.p was not significantly higher than that in P3.p. Surprisingly, the LIN-39 level was the highest in P5.p and decreased from P5.p to P8.p. At a later developmental time (late L2 larvae), as previously reported, the LIN-39 peak was found on P6.p.
Analysis of wild-type worms showed that eff-1p::GFP was expressed in the daughter cells of P3.p, P4.p, and P8.p that are committed to fusion, and was absent in the daughter cells of P(5-7).p which escape the fusion fate.
All Pn.p cells express the transgene. During L3, the VPCs divide to form two daughters that both stain positive. The two daughters continue to divide and form first four cells and then 8 cells for P6.p, and seven cells for P5.p and P7.p. All of these stain throughout divisions. The staining observed in the daughters of P3.p, P4.p and P8.p is significantly weaker than observed in P5-7.p.
Before vulval induction occurs, lin-39 was expressed uniformly in the VPCs. At the time of vulval induction, lin-39 expression increased dramatically in P6.p. P3.p, P4.p, and P8.p showed the lowest levels of lin-39 expression.
Similar expression patterns were obtained using either the BAR-1 antibodies in immunocytochemistry experiments or by direct observation of the functional BAR-1-GFP. BAR-1 is present in P3.p through P8.p in the late L1/early L2 stage and disappears in the mid-L3 stage before the first divisions of P3.p-P8.p. Did not observe BAR-1 in P1.p, P2.p, P9.p, P10.p or P11.p at this time. P6.p occasionally showed higher BAR-1 expression than the other vulval precursor cells, and was often observed to be the last vulval precursor cell to lose BAR-1 staining. In addition to the vulval precursor cells, BAR-1 is expressed in several other postembryonic cells, including the seam cells , cells in the somatic gonad and P12.