Worm Breeder's Gazette 4(1): 33
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We have described 11 temperature-sensitive abnormal embryogenesis mutants (Miwa et al.). Here we describe the cellular phenotype of these mutants at the permissive (16 C ) and non-permissive temperature (25 C ), including the temperature-sensitive phase of embryogenesis, visible developmental defects and cell lineages (time and direction of cell divisions and cell migrations at 16 C and 25 C ) at least to the 50-cell stage (or stage of arrest). All but one mutant have visible developmental defects at 25 C before the stage of arrest. The six mutants that arrest at the beginning of the morphogenesis phase ( between the lima bean and tadpole stages) have defective developmental events or abnormal cell lineages before the 50-cell stages, yet they continue developing abnormally for several hours. Some mutants also have visible defects at 16 C. The overall division rate of the stem- cell lines of the mutants at 25 C (excluding the 2 one-cell stage stoppers and the osmotically sensitive mutant) is faster than in the wild-type in 2 mutants, slower in 5 mutants, and equal to the wild- type in one mutant. The temperature-sensitive phase of embryogenesis (TSPh), as defined by shift-up experiments of eggs in different stages, for 5 maternal mutants (4 genes, emb-1, emb-6, ore the two-cell stage, and in 4 mutants (3 genes, emb-2, emb-9) the TSPh ends during embryogenesis; the TSPh for 2 mutants (genes emb-4, t be determined because the eggs did not survive handling for microscopy. Both alleles in gene emb-5 (maternal) have a defective gastrulation ( time of E-cell migration and time and direction of E-cell division) and they arrest around the lima bean stage. The TSPh of one allele ends at the 12-cell stage and that of the other ends at the 50-cell stage. The severity of the gastrulation defect is also different in the two mutants. The TSPh of the only zygotic mutant (emb-9) is between the comma and the early pretzel stage, and it stops in the pretzel stage without any visible abnormality. The cell lineage of this mutant at 25 C is normal to the 100-cell stage and it has no visible defects up to this stage.