RNAi-mediated silencing of JNK signaling components—including D-JNKK/Hemipterous (Hep), D-JNK/Basket (Bsk) and D-Fos/Kayak (Kay) (Fig 5A), in the cyst cell lineage via the eyaA3ts system at 29°C markedly suppressed ectopic Zfh-1 expression in the testes of mated males, as also found for overexpression of dominant-negative Bsk (referred to as BskDN) (Fig 6A). The gene discussed is FOS; the disease is cyst.