The bit1-1 mutation affects the ERN-1 transcription factor required for nodulation and the initiation of infection threads (Middleton et al., 2007) and the nsp2-2 mutation affecting a GRAS domain transcription factor, causes defects in infection and cortical cell division following inoculation with Sinorhizobium meliloti (Oldroyd & Long, 2003). The gene discussed is ERN1; the disease is infection.