Worm Breeder's Gazette 16(2): 48
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.
| 1 | Institut J. Monod, Paris, France |
| 2 | Caltech, Pasadena, USA |
Oscheius / Dolichorhabditis sp. CEW1 and Pristionchus pacificus (R. Sommer lab) have been chosen to study the evolution of vulva formation in comparison to Caenorhabditis elegans. We have performed in Oscheius sp. CEW1 a random F2 screen for Egl and marker mutations (EMS mutagenesis of approx. 50,000 gametes).
The range of morphological markers isolated is similar to C. elegans: Unc
(Kinker, Twitcher, Sluggish and Coilers), Dpy, Rol, Lon, as well as 2 Him (1 recessive,
1 dominant). Complementations and linkage analysis are under progress; 5 autosomal
linkage groups have been defined to date but we do not know whether they represent
5 chromosomes. Some of the mutations presented here are allelic (for example the
4 Twitchers).
| C. elegans (1) | Oscheius sp. CEW1 | P. pacificus (2) | |||||||
| A | X | % | A | X | % | A | X | % | |
| Dpy | 79 | 29 | 27% | 22 | 1 | 4% | 24 | 0 | 0% |
| Unc | 212 | 100 | 32% | 18 | 26 | 59% | 21 | 2 | 9% |
| Rol | 4 | 1 | - | 0 | 5 | - | 1 | 0 | - |
| Lon | 5 | 5 | - | 1 | 1 | - | 0 | 0 | - |
| Total | 300 | 135 | 31% | 41 | 33 | 45% | 45 | 2 | 5% |
Oscheius, like C. elegans and Pristionchus (2), is hermaphroditic
with spontaneous males, appears to have a XX/XO sex determination (as judged from
genetic data) and 6 chromosomes (as judged by Hoechst staining of oocytes). In C.
elegans (1), 31 % of the markers are located on the X chromosome, which only
represents 18% of the physical genome and 14% of the genes (3). In Oscheius,
45 % of the markers are located on the X chromosome. Conversely, in P. pacificus,
almost all isolated markers are located on autosomes (2). We wonder whether
the efficiency of mutagenesis is X- and species-specific.
Strangely, this excess of X-linked markers is very unequally shared between Dpys and Uncs in Oscheius (but not in C. elegans). The Dpys are mainly located on autosomes, but 59 % of the Uncs are X-linked (we do not know how many are allelic). We do not understand this strange bias. Maybe there are some mutational hotspots in Oscheius on X-linked unc genes; or many unc genes on theX chromosome.
(1) Brenner, S. (74), Genetics, vol 77, 71-94.
(2) Sommer, R. et al (96), Fundam. appl. Nematol., vol 19, 511-521.
(3) Consortium (98), Science, vol 282, 2012-2028.