Germ-line regulation of the Caenorhabditis elegans sex-determining gene tra-2.
The Caenorhabditis elegans sex-determining gene tra-2 promotes female development of the XX hermaphrodite soma and germ line. We previously showed that a 4.7-kb tra-2 mRNA, which encodes the membrane protein TRA-2A, provides the primary feminizing activity of the tra-2 locus. This paper focuses on the germ-line activity and regulation of tra-2. First, we characterize a 1.8-kb tra-2 mRNA, which is hermaphrodite-specific and germ-line-dependent. This mRNA encodes TRA-2B, a protein identical to a predicted intracellular domain of TRA-2A. We show that the 1.8-kb mRNA is oocyte-specific, suggesting that it is involved in germ-line or embryonic sex determination. Second, we identify a tra-2 maternal effect on brood size that may be associated with the 1.8-kb mRNA. Third, we investigate seven dominant tra-2(mx) (for mixed character) mutations that sexually transform hermaphrodites to females by eliminating hermaphrodite spermatogenesis. Each of the tra-2(mx) mutants possesses a nonconserved missense change in a 22-amino-acid region common to both TRA-2A and TRA-2B, called the MX region. We propose that the MX region mediates a posttranslational regulation of tra-2 essential for the onset of hermaphrodite spermatogenesis. Finally, we discuss aspects of tra-2 function and regulation that are specific to the unusual control of cell fate in the hermaphrodite germ line.
Kuwabara
P E
PE
MRC Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 2QH, United Kingdom.
Okkema
P G
PG
Kimble
J
J
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000196:embryology / Q000235:genetics*; D029721:Drosophila Proteins; D005260:Female; D018507:Gene Expression Regulation, Developmental; D008297:Male; D008969:Molecular Sequence Data; D009866:Oogenesis / Q000235:genetics; D012261:Ribonucleoproteins / Q000235:genetics*; D016415:Sequence Alignment; D019849:Sex Determination Processes; D013091:Spermatogenesis / Q000235:genetics
D029721:Drosophila Proteins; D012261:Ribonucleoproteins; C066174:tra2 protein, Drosophila