Worm Breeder's Gazette 13(2): 36 (February 1, 1994)

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.

A Variety of Synthetic Dauer-constitutive Mutations

Isao Katsura[1], Norio Suzuki[2], Takeshi Ishihara[3]

[1]DNA Research Center, National lnstitute of Genetics, and School of Life Science, Graduate University of Advanced Studies, Mishima, Shizuoka-ken 411, Japan
[2]DNA Research Center, National lnstitute of Genetics, Mishima, Shizuoka-ken 411, Japan
[3]DNA Research Center, National lnstitute of Genetics, and School of Life, Mishima, Shizuoka-ken 411, Japan

We wonder why there is no mutation having Daf Unc phenotype, although we may expect such phenotype for many general neuronal mutations. The key seems to be that there are mutations having Unc synthetic Daf phenotype. So far the following double mutants are reported to be dauer-constitutive (Daf-c): unc-31 ; unc-3 (1), unc31 ; aex-3 (1,2), unc-104 ; osm-1 , unc-104 ; che-11 ,and unc-104 ; che-13 (3). We therefore looked for more synthetic Daf-c's among known mutations.

The following combinations of mutations were found to have synthetic Daf-c phenotype, although the penetrance is incomplete in most cases: (I) one of the flr mutations in combination with unc-3 or unc-31 ,(2) egl-4 ; unc-3 and egl-32 ; unc-3 ,(3) one of the dauer-defective (Daf-d) cillium structure mutations (ref.4,5) in combination with unc-31 or unc-3 ,and (4) WIC-31 ; daf-6 (Table 1).

The results show that the flr (fluoride-resistant) mutations (ref.6) are related to

neuronal functions. It is natural that egl-4 and egl-32 are synthetic Daf. Their Egl phenotype is suppressed by daf-3 (7), and in this sense they resemble daf-1 , daf-4 , daf-7 , daf-8 ,and daf-14 ,which are also Egl (7) and whose Daf-c and Egl phenotypes are suppressed by daf-3 (5,7,8). We are testing if the Daf-c phenotypes of the various double mutants are suppressed by daf-3 or daf-12 .

Furthermore, we have isolated more than forty synthetic Daf-c alleles from about 5,000 F2 of EMS-mutagenized unc-31 ( e169 )Ex[ unc-31 (+)]*worms by selecting for those which segregate Unc dauers but no Unc+ dauers at 25°. We are now mapping them.

In general, synthetic phenotype implies redundancy in functions of molecules, pathways or cells. We think the synthetic Daf-c phenotype is probably related to redundant neural circuits for chemosensory signals. Especially interesting is that mutations in the cillium structure genes and daf-6 have both Daf-d and synthetic Daf-c phenotypes, which cannot be explained by a serial pathway (Fig.1a) used for the conventional theory of epistasis. However, it can be explained by a parallel pathway (Fig. 1b) containing both positive and negative control (I. Katsura, unpublished results).

(references) (I) C.I.Bargmann et. al.: CSHSQB 60, 529 (1990)

(2) L.Avery: Genetics 133, 897 (1993)

(3) J.Vowels & J.Thomas: WBG 12(2) p85 (1992)

(4) L.Perkins et al.: Dev. Biol. 117, 456 (1986),

(5) J.Vowels & J.Thomas: Genetics I30 ,105 (1992)

(6) I.Katsura et al.: Genetics 136, in press (1994), (7) C.Trent et al.: Genetics 104, 619 (1983)

(8) D.L.Riddle et al.: Nature 290, 268 (1981)

*: made in our laboratory by injection of the cosmid C14G10 (containing unc-31 gene; D.Livingstone & R.Hoskins, cited in L.Avery et al.: Genetics 134, 455(1993))

Literature Cited:

(I) C.I.Bargmann et. al.: CSHSQB 60, 529 (1990)