Fig 7. Model of the proposed function of RALPH effectors in the interaction between powdery mildews and host plants.

A) Plants recognise potential pathogenic microbes by inducing defence responses, such as the production of the jasmonate-induced protein (JIP60) mediated by methyl jasmonate (MeJA). JIP60 is a ribosome-inhibiting protein (RIP) that degrades host ribosomes and triggers cell death. Host cell death is lethal for obligate biotrophic pathogens such as B. graminis. B) Powdery mildew fungi secrete abundant RNase-like proteins from their haustoria (RALPH effectors), such as CSEP0064/BEC1054. We hypothesise that RALPHs facilitate maintenance of live host cells by competing with the host suicide mediated by RIPs such as JIP60.