CA4 and infection: Strikingly, we found that both effectors are capable of degrading cA4, suggesting that this CAAD-Csx1 pair may be cross-regulated and achieve immunity through a dual-targeting mechanism: in response to infection, Csx1 degrades viral RNA while CAAD disrupts nucleotide metabolism via ATP deamination, which can be relieved via cA4 degradation when infection has been eliminated.