Vulva formation in the nematode Caenorhabditis elegans serves as an iconic system in developmental biology to understand how inductive signals and cellular competence coordinate tissue patterning. Laser ablation experiments targeting the anchor cell and hypodermal (vulval precursor) cells have defined critical components and mechanisms responsible for specifying vulval fate.

Interpreting Key Experiments on Vulva Formation

Researchers carried out targeted laser ablation, selectively destroying the anchor cell or combinations of six hypodermal vulval precursor cells, to decipher vulval development:

• Ablating the anchor cell prevents vulva formation: This shows that the anchor cell is essential for inducing vulva fate—without its signal, the neighboring hypodermal cells (precursors) default to an alternative, non-vulval fate.

• Ablating all six vulval precursor cells: This leads to no vulva, confirming these are the only cells competent for vulva formation.

• Ablating the three central precursor cells (normally selected for vulva formation): The more distal cells, which usually form other tissues, can assume the vulval fate, demonstrating both their competence and the equivalence group property—the ability of any of these six cells to be induced under the right circumstances.

Analyzing the Statements

Let’s match the experimental observations to the provided statements:

A. Anchor cell acts as an inducer: Directly supported—the anchor cell’s removal blocks vulva induction, identifying its pivotal inductive role.
B. Six hypodermal cells with potential form an equivalence group: Confirmed by the experiment where outer cells adopt vulval fate if inner ones are destroyed—defining the equivalence group.
C. Three out of six hypodermal cells participate in vulva formation: Supported by normal development—only three cells are normally recruited, though any of the six can replace them if necessary.
D. The central cell functions as the 1° cell and the two lateral as 2° cells: While true in normal development, this is not an immediate result of these particular ablation experiments; it requires further lineage analysis.
E. The 1° cell secretes a short-range juxtacrine signal: This detail about signaling between specific vulval cells is a mechanistic insight, not directly demonstrated by the ablation results described.

Correct Combination: Experimental Derivations

The statements that can be clearly derived from the described experimental results are:

• A. Experimental removal indicates anchor cell is the inducer.

• B. The ability of any of the six cells to substitute for the others confirms the equivalence group.

• C. Normally, three out of six cells become vulval cells; others can serve this purpose if needed.

Thus, the correct answer is:

(1) A, B and C