Probable nucleotidyltransferase that catalyzes the formation of cyclic dinucleotide second messenger in response to some unknown stimulus (By similarity). Does not catalyze the formation of cyclic GMP-AMP from ATP and GTP (PubMed:34261128). Activated in response of some unknown stimulus (PubMed:29924997). Not activated in response to L-monocytogenes infection (PubMed:29924997). Flies display a normal antiviral immune response. Belongs to the mab-21 family.