8. A group of 3 cells, the P6p, P5p and the anchor cell are clustered together in the
C.elegans hypodermis. Normally the P6p cell gives divides 3 times and forms the
vulva. You find that if the P6p cell is destroyed, the P5p divides and will form the
vulva. If the anchor cell is destroyed, neither the P6p cell nor the P5p cell form the
vulva. How do you interpret this data?
a. The anchor cell inhibits the P6p from forming a vulva.
b. The anchor cell induces vulval formation by the P6p cell.
c. The P6p cell inhibits vulval formation by the anchor cell.
d. The P5p cell induces vulval formation by the P6p cell.

C. elegans Vulva Development: Anchor Cell P6p P5p MCQ Solved

The anchor cell induces vulval formation in C. elegans by signaling to nearby hypodermal precursor cells like P6p, which normally divides to form the vulva. Destroying P6p allows P5p to compensate, showing equivalence among precursors, while anchor cell ablation blocks vulva formation entirely. This data supports inductive signaling from the anchor cell as the key mechanism.​

Correct Answer

b. The anchor cell induces vulval formation by the P6p cell.​

Option Analysis

Classic laser ablation experiments reveal cell interactions in vulva development. The anchor cell secretes LIN-3 (EGF-like signal) to induce nearby vulval precursor cells (VPCs) via LET-23 receptor and Ras/MAPK pathway.​​

• a. The anchor cell inhibits the P6p from forming a vulva. Incorrect. Anchor cell destruction prevents vulva formation by both P6p and P5p, indicating activation rather than inhibition.​

• b. The anchor cell induces vulval formation by the P6p cell. Correct. P6p normally receives the strongest inductive signal and divides into vulval tissue; without anchor cell, no induction occurs.​

• c. The P6p cell inhibits vulval formation by the anchor cell. Incorrect. Anchor cell signals first to induce VPCs; P6p lacks evidence of inhibiting anchor cell function.​​

• d. The P5p cell induces vulval formation by the P6p cell. Incorrect. P5p substitutes only after P6p destruction, but neither forms vulva without anchor cell signal, ruling out P5p as primary inducer.​

In C. elegans vulva development, the anchor cell plays a central inductive role for P6p and P5p hypodermal cells to form vulval tissue, a key CSIR NET Life Sciences topic. This classic experiment demonstrates inductive signaling and cell equivalence through targeted ablations.​

Vulva Precursor Cells Role

Six VPCs (P3.p-P8.p) form an equivalence group, but P5p, P6p, P7p normally contribute. P6p adopts 1° fate (primary vulva), P5p/P7p 2° fate via LIN-12/Notch lateral inhibition after anchor cell LIN-3 induction.​

• Anchor cell ablation: All VPCs default to 3° hypodermal fate.​

• P6p ablation: P5p adopts 1° fate, proving competence.​

Mechanism Overview

Anchor cell LIN-3 gradient activates LET-23/Ras in closest VPC (P6p), promoting proliferation. Lateral signals ensure fate diversity. Relevant for CSIR NET questions on developmental signaling pathways.​