Worm Breeder's Gazette 8(2): 50
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.
We have analyzed the arrangement of Tc1 elements in several highcopy- number strains. Most of these strains originated from the C. elegans laboratory in Lyon, France, and hence could be clonally related. This group includes Bergerac (BO) (CGC), Bergerac (FR) (CGC), BL1 (formerly our 'Bergerac (SH)' from Bill Sharrock), and N62 (MRC). One new wild isolate from California, DH424 (formerly EPC4), also has a large number of Tc1 elements in its genome. We have found that Tc1 is arranged similarly in all these strains. We have used a two-dimensional system to visualize individual restriction fragments carrying Tc1 elements. DNA was digested with one enzyme and fractionated on a sucrose gradient. DNA from the upper one-third of the gradient was collected, digested with a second enzyme and analyzed for Tc1 elements on a Southern. By this means about 80 distinct bands were visualized. The five strains analyzed had about 70 fragments in common, and from five to 15 unique fragments. Interestingly, DH424 was not distinct from the Bergerac group. In fact, reckoning up similarities and differences, it was more closely related to FR, BL1 and N62 than to BO. Either the amplification of Tc1 must have occurred before the separation of the DH424 and Bergerac lineages, or Tc1 has a strong preference for inserting at certain sites in the genome. We also compared the structure of the Tc1 elements themselves in these strains and found no differences. By doing a Southern after double digestion with Eco RV (which cuts within the inverted repeats 20 base pairs from the ends of Tc1) and a second enzyme, it is possible to construct a consensus restriction map of genomic elements. In all these strains Tc1 elements are 1.6 kb in length and have similarly-placed SalI and XhoI sites.