TABLE 4

Summary of MPK-1 germline functions, associated phenotypes, and site of action

MPK-1 germline functions
Pachytene progressionPachytene cellular organizationOocyte organization and differentiationOocyte growth controlOocyte nuclear migrationOocyte maturation and ovulationSpecification of male fateaPromotion of proliferative fate (nonessential)
mpk-1 lf phenotypeNuclei arrested in pachyteneGaps or absence of cells on the surface of the gonad, loss of rachisDisorganized shape/position of oocytes, multinucleate oocytesLarge oocytesCentrally located oocyte nucleusDelayed or failed maturation and ovulation; EmoFeminized hermaphrodite and male germlinesEnhancement of glp-1(bn18) premature meiotic entry
Site of mpk-1 functionGermlinebGermlinebGermlinecGermlinecGermlinecLikely germlinedGermlinecGermlinec
Pathway genes known to be involved in processlet-60, ksr-2, lin-45, mek-2let-60, ksr-2, lin-45, mek-2let-60, ptp-2lin-45, mek-2lin-45, mek-2
  • a It is not currently known if let-60 and ksr-2 function in male germline sex determination. For the let-60(dx16) allele, which is a genetic and molecularly null (see supplemental Table 8 and legend at http://www.genetics.org/supplemental/), adult hermaphrodite escapers of L1 lethality make sperm followed by pachytene-arrested cells, suggesting that let-60 does not function in promoting the male germ cell fate. However, as a number of germline sex determination genes show maternal effects (e.g., Doniach and Hodgkin 1984), we cannot rule out the possibility that the male germ cells produced in let-60(dx16) homozygotes are a consequence of maternally supplied let-60(+). Similarly, ksr-2 null mutant hermaphrodites make sperm (Ohmachi et al. 2002), which could also be a result of maternal rescue. Male germ cell fate specification in let-60 and ksr-2 null XO male mutants has not yet been examined.

  • b Mosaic analysis from Church et al. (1995) and RNAi in rrf-1(pk1417) null (supplemental Table 1 at http://www.genetics.org/supplemental/).

  • c RNAi in rrf-1 null (supplemental Tables 1, 4, 5, and 7).

  • d Based on (1) Emo phenotype following RNAi in rrf-1 null and (2) strong dpMPK-1 staining in proximal oocytes in hermaphrodites but not in females. However, since time-lapse video analysis has not been performed to determine the basis of the Emo phenotype and because dpMPK-1 is detected in sheath cell nuclei, we cannot rule out that MPK-1 may also function in sheath cells to promote maturation/ovulation.