Cytoplasmic poly(A) RNA polymerase that adds successive AMP monomers to the 3'-end of specific RNAs, forming a poly(A) tail. The enzymatic activity is enhanced by its interaction with gls-1. Required, together with gld-2, for early meiotic progression in male and female germ cells and for gld-1 protein accumulation in the hermaphrodite germline. In the germline, forms a complex with gls-1 which directly binds to gld-1 mRNA and prevents its degradation. ATP + RNA(n) = diphosphate + RNA(n)-3'-adenine ribonucleotide Interacts with gls-1 isoform C. Localizes to P granules. This association is less apparent during pachytene, becomes obvious in maturing oocytes and is most prominently visible in developing embryos. Germline-specific. Expressed both maternally and zygotically throughout embryonic development and in adult hermaphrodites. In contrast to other poly(A) RNA polymerases, lacks any RNA-binding domain. High embryonic lethality. Hermaphrodite animals are partially fertile and those that produce sperm and oocytes have reduced brood sizes and display smaller germlines. Hermaphrodite gld-4 and gld-2 double mutants are fully sterile and display either an earlier meiotic arrest than gld-2 single mutant or a failure to commit to meiotic progression and a return to mitosis. The gld-4 locus produces a single transcript that is SL-1 trans-spliced.