Despite the high number of MAPK genes, MAPK pathways of higher plants were studied less than animal or fungal ones. Although their signaling appears very complex, the MPK3, MPK4 and MPK6 kinases of Arabidopsis thaliana are key mediators of responses to osmotic shock, oxidative stress, response to cold and involved in anti-pathogen responses. Asai et al. 2002s model of MAPK mediated immunity passes the effector recognition signal from FLS2 ⇨ MEKK1 ⇨ MKK4 or MKK5 ⇨ MPK3 and MPK6 ⇨ WRKY22 or WRKY29. However the work of Mészáros et al. 2006 and Suarez-Rodriguez et al.' 2007 give other orders for this pathway and it is possible that these are parallel pathways operating simultaneously. They are also involved in morphogenesis, since MPK4 mutants display severe dwarfism.