Worm Breeder's Gazette 14(4): 43 (October 1, 1996)
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.
MPI fuer Entwicklungsbiologie, Spemannstrasse 35, 72076 Tuebingen, Germany
Several aspects of cell fate specification during vulval development differ between Caenorhabditis and Pristionchus. Two of the six cells that correspond to the Caenorhabditis vulval equivalence group die by programmed cell death in Pristionchus. Another cell fuses with the epidermis early in development, making it incompetent to form vulval tissue. A third evolutionary change of cell fate exists, as another cell has only limited developmental potential and can adopt the 2o but not the 1o fate. In Caenorhabditis, all six vulval precursor cells (VPCs) are multipotent, i.e. they can adopt all three cell fates. Thus, in a group of six cells, three evolutionary alterations of cell fate specification occurred between the two species. To determine if the observed changes of cell fate specification between Pristionchus and Caenorhabditis evolved independently, species of six additional genera of the Diplogastridae have been studied. Comparative studies of cell lineage and pattern formation during vulval development in the species Diplogaster maupasi, Koerneria sp., Diplogasteroides sp., Pseudodiplogasteroides sp., Aduncospiculum halicti and Goodeyus ulmi have been carried out. All species display an identical differentiation pattern of ventral epidermal cells as revealed by cell lineage analysis. Despite these morphological similarities, cell ablation experiments suggest differences in the underlying pattern formation processes. In four species (Koerneria, Diplogasteroides, Pseudodiplogasteroides and Aduncospiculum), the cell (P7.p) that has limited developmental potential in Pristionchus, can adopt either vulval cell fates. In two species (Koerneria and Diplogasteroides), P8.p, the cell that is incompetent in Pristionchus, is competent in a manner similar to the corresponding cell in Caenorhabditis. Furthermore, in Diplogaster and Goodeyus, some VPCs show differentiation properties in the absence of gonadal inductive signal. The finding that the pattern of cell competence varies among species indicates that developmental mechanisms can change during evolution while differentiation pattern remain invariant.