title: Conservation of MAP kinase activity and MSP genes in parthenogenetic nematodes.
abstract: BACKGROUND
  MAP (mitogen-activated protein) kinase activation is a prerequisite for oocyte maturation, ovulation and fertilisation in many animals. In the hermaphroditic nematode Caenorhabditis elegans, an MSP (major sperm protein) dependent pathway is utilised for MAP kinase activation and successive oocyte maturation with extracellular MSP released from sperm acting as activator. How oocyte-to-embryo transition is triggered in parthenogenetic nematode species that lack sperm, is not known.
  
  
  RESULTS
  We investigated two key elements of oocyte-to-embryo transition, MSP expression and MAP kinase signaling, in two parthenogenetic nematodes and their close hermaphroditic relatives. While activated MAP kinase is present in all analysed nematodes irrespective of the reproductive mode, MSP expression differs. In contrast to hermaphroditic or bisexual species, we do not find MSP expression at the protein level in parthenogenetic nematodes. However, genomic sequence analysis indicates that functional MSP genes are present in several parthenogenetic species.
  
  
  CONCLUSIONS
  We present three alternative interpretations to explain our findings. (1) MSP has lost its function as a trigger of MAP kinase activation and is not expressed in parthenogenetic nematodes. Activation of the MAP kinase pathway is achieved by another, unknown mechanism. Functional MSP genes are required for occasionally emerging males found in some parthenogenetic species. (2) Because of long-term disadvantages, parthenogenesis is of recent origin. MSP genes remained intact during this short interval although they are useless. As in the first scenario, an unknown mechanism is responsible for MAP kinase activation. (3) The molecular machinery regulating oocyte-to-embryo transition in parthenogenetic nematodes is conserved with respect to C. elegans, thus requiring intact MSP genes. However, MSP expression has been shifted to non-sperm cells and is reduced below the detection limits, but is still sufficient to trigger MAP kinase activation and embryogenesis.
authors.affiliation: Zoological Institute, University of Cologne, Köln, Germany. peter.heger@uni-koeln.de
authors.forename: Peter
authors.initials: P
authors.lastname: Heger
authors.forename: Michael
authors.initials: M
authors.lastname: Kroiher
authors.forename: Nsah
authors.initials: N
authors.lastname: Ndifon
authors.forename: Einhard
authors.initials: E
authors.lastname: Schierenberg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology / Q000378:metabolism*; D047108:Embryonic Development; D015801:Helminth Proteins / Q000737:chemistry / Q000235:genetics*; D008540:Meiosis; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008969:Molecular Sequence Data; D009348:Nematoda / Q000196:embryology / Q000378:metabolism*; D010312:Parthenogenesis; D016415:Sequence Alignment
chemical_list: D015801:Helminth Proteins; C050602:major sperm protein, nematode; D020928:Mitogen-Activated Protein Kinases