Worm Breeder's Gazette 12(3): 100 (June 15, 1992)
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 isolated a maternal effect mutation that causes animals to arrest normal development in abundant food either as dauers or as late larvae or sterile adults which retain some dauer-like properties. Homozygous mg44 progeny from heterozygous parents appear completely normal. In addition, the mutant phenotype of progeny from mg44 homozygotes can be rescued zygotically suggesting that this gene may function relatively late in development. As is characteristic of many genes involved in dauer formation, temperature has a modulatory effect on the mutant phenotype. At 25°C, progeny of homozygous mg44 hermaphrodites arrest at the "L3" stage either as fully-formed, SDS resistant dauers or as larvae which exhibit features intermediate between a dauer and an L3 (a darkly-staining intestine characteristic of dauers but no dauer alae and the pharynx is variably slimmed-down and occasionally pumps). At 15°C and 20°C, mg44 homozygotes produce progeny that initially arrest with a phenotype similar to that described above at 25°C, but then continue to develop, arresting as either L4 'sor sterile adults. These adults make adult alae and the arms of the gonad have reflexed but do not elongate to the extent of normal adults and no oocytes are made. And, like dauers, the intestines of these sterile animals remain extremely dark. Also, many of the worms that arrest as adults have a protruding vulva. The mutant, mg44 ,maps to chromosome II near a previously-identified maternal effect, non-conditional dauer constitutive, daf-23 (Riddle, 1988, worm book). We are currently testing whether these two genes are allelic.
Preliminary data on the phenotype of double mutants of mg44 and several dauer defective genes are as follows: daf-3 ( e1376 ), daf-12 ( m20 ),and che-3 ( e1379 )do not suppress mg44 while daf-16 ( m27 )does suppress mg44 .These epistasis results together with the unusual arrest phenotype suggest that mg44 and perhaps daf-2 (see below), constitute a new class of genes that is required for non-dauer or continuous development for the following reasons. First, while it is known that the conditional dauer constitutives daf-1 , daf-4 , daf-7 , daf-8 , daf-1 l and daf-14 are suppressed by mutations in daf-3 and daf-12 , daf-2 and mg44 are not suppressed. Second, while it has been shown that double mutants between daf-16 and the conditional dauer constitutives listed above lead to the formation of partial dauers, daf-16 appears to suppress dauer formation in both mg44 and daf-2 mutants as well as the L4 arrest and adult sterile phenotype of mg44 .However, it is unlikely that daf-16 is functioning directly downstream of daf-2 since daf-16 ; daf-2 ; daf-12 triple mutants arrest with a daf-2 ; daf-12 phenotype. Interestingly, we had shown previously that daf-16 has an additional unusual interaction with the dauer constitutive gene daf-2 .Specifically, daf-16 ; daf-2 double mutants form precocious dauers (~4 hours earlier than daf-2 alone) which then recover. We have not yet determined whether a similar phenomenon is occurring with mg44 .And finally, as observed by Vowels and Thomas, (Genetics, 130:105, 1992), daf-2 ; daf-12 double mutant worms appear to be unable to develop as either dauers or non-dauers. Based on their observation, Vowels and Thomas suggested that daf-2 may be required for development to L3 .We propose that mg44 and daf-2 may act in the same pathway, directing nondauer development. daf-16 ,which is epistatic to both of these genes, may have the role of insuring that worms maintain dauer under dauer-inducing conditions.
Genetics, 130:105, 1992