Worm Breeder's Gazette 10(3): 127
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
To investigate the evolution of developmental control mechanisms, I have begun a comparative study of vulval induction. I have started with the Shanghai-1 nematode strain, provided by Chris Link, because, like C. elegans, Shanghai-1 has hermaphrodites and functional males, and therefore might be suitable for genetic studies. Vulval development in this species differs from that in C. elegans in all but the P6.p lineage. P6.p generates a [TTTT] lineage (where T represents a Transverse division axis), as in C. elegans. P5.p and P7.p generate [UUUU] lineages (where U stands for Undivided Pn.pxx nucleus). P4.p and P8.p (and often, P3.p) generate [SSSS] lineages ( where S represents a Syncytial hypodermal nucleus). To examine the cell-cell interactions underlying vulval development in this strain I carried out a small set of ablation experiments. Vulval Induction: In three animals in which the gonad primordium was destroyed and in two in which both Z1 and Z4 were destroyed, no vulva was formed. Therefore, the gonad induces the vulva. In these animals, P(4-8).p generated four progeny that appeared to fuse with the large hypodermal syncytium, indicating that the ground state of these cells is to generate four S nuclei. In half the animals, P3.p did not divide, but rather fused with the syncytium; in the other half, P3.p generated four S progeny. Regulation: So far, after ablation of one or more Pn.p cells,I have seen P4.p generate a [UUUU] and a [TTTT] lineage, and P5.p generate a [TTTT] lineage. As described above, P4.p and P5.p can also generate [SSSS] lineages. These observations indicate that P4.p and P5.p are tripotent, and that the vulval equivalence group comprises at least P( 4-7).p. The limited data are consistent with [TTTT] being primary; [UUUU] secondary, and [SSSS] tertiary. One animal which had only a single [TTTT] lineage and no [UUUU] lineages was egg-laying proficient (Egl+), indicating that as in C. elegans and P. redivivus, the progeny of the primary lineage are sufficient to form a functional vulva. Production of the anchor cell: To investigate whether Shanghai-1 is more like C. elegans or like P. redivivus with respect to anchor cell regulation, I destroyed Z1 in one hermaphrodite and Z4 in another. In both animals, an anchor cell was produced in a monodelphic gonad, and a normal vulva was induced. These observations suggest that either Z1 or Z4 can produce an anchor cell, as is the case in C. elegans.To examine the feasibility of genetic studies with this organism, I carried out two pilot 40-plate mutageneses. Because Shanghai-1 hermaphrodites are somewhat egg-laying defective (Egl-) to begin with, I thought it would be impossible to obtain Egl- animals (I was hoping for Muvs), but this is not the case. Besides the usual assortment of Dpys and Uncs, only a few of which I kept, I obtained one Egl- strain. This defect is due at least in part to a defect in vulval morphogenesis.