It was previously shown that the Raf/MEK/ERK MAPK pathway is necessary and sufficient for the Dar response: hyper activation of the pathway by the over expression of constitutively active forms of LIN-45 (Raf), MEK-2 (MEK), or MPK-1 (ERK) results in tail swelling in the absence of infection (as we have shown for constitutively active EGL-30* and RHO-1*), while mutations in lin-45, mek-2 or mpk-1 result in a defective Dar response [42]. The gene discussed is MAP2K7; the disease is infection.