Specification of Germ Cell Fates by FOG-3 Has Been Conserved During Nematode Evolution

• Published in: Genetics (Austin) 2001-08, Vol.158 (4), p.1513-1525
• Main Authors: Chen, Pei-Jiun, Cho, Soochin, Jin, Suk-Won, Ellis, Ronald E
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animal reproduction; Animals; Base Sequence; Binding Sites; Biological Evolution; Blotting, Northern; Caenorhabditis - classification; Caenorhabditis - genetics; Caenorhabditis - physiology; Caenorhabditis briggsae; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Caenorhabditis remanei; Cell Lineage; Cells; Cellular biology; Evolution; Female; fog-3 gene; FOG-3 protein; Gender; Genetics; Helminth Proteins - genetics; Helminth Proteins - physiology; Male; Models, Genetic; Molecular Sequence Data; Oocytes - metabolism; Pedigree; Phylogeny; Polymerase Chain Reaction; Promoter Regions, Genetic; Protein Structure, Tertiary; Reverse Transcriptase Polymerase Chain Reaction; RNA - metabolism; Sequence Homology, Amino Acid; Sequence Homology, Nucleic Acid; Sex Determination Processes; Species Specificity; Spermatogenesis; TRA-1A protein; Worms
• ISSN: 0016-6731; 1943-2631; 1943-2631
• DOI: 10.1093/genetics/158.4.1513

Rapid changes in sexual traits are ubiquitous in evolution. To analyze this phenomenon, we are studying species of the genus Caenorhabditis. These animals use one of two different mating systems-male/hermaphroditic, like the model organism Caenorhabditis elegans, or male/female, like C. remanei. Since hermaphrodites are essentially females that produce sperm for self-fertilization, elucidating the control of cell fate in the germ line in each species could provide the key to understanding how these mating systems evolved. In C. elegans, FOG-3 is required to specify that germ cells become sperm. Thus, we cloned its homologs from both C. remanei and C. briggsae. Each species produces a single homolog of FOG-3, and RNA-mediated interference indicates that FOG-3 functions in each species to specify that germ cells develop as sperm rather than as oocytes. What factors account for the different mating systems? Northern analyses and RT-PCR data reveal that the expression of fog-3 is always correlated with spermatogenesis. Since the promoters for all three fog-3 genes contain binding sites for the transcription factor TRA-1A and are capable of driving expression of fog-3 in C. elegans hermaphrodites, we propose that alterations in the upstream sex-determination pathway, perhaps acting through TRA-1A, allow spermatogenesis in C. elegans and C. briggsae XX larvae but not in C. remanei.