Plant SYP12 syntaxins mediate an evolutionarily conserved general immunity to filamentous pathogens

Filamentous fungal and oomycete plant pathogens that invade by direct penetration through the leaf epidermal cell wall, cause devastating plant diseases. Towards non-adapted filamentous pathogens, plant pre-invasive immunity is highly effective and durable. Pre- and post-invasive immunity correlates with the formation of evolutionarily conserved and cell-autonomous cell wall structures, named papillae and encasements. Yet, it is still unresolved how papillae/encasements are formed and whether these defense structures prevent pathogen ingress. Here we show that inArabidopsis, the two closely related members of the SYP12 clade of syntaxins (PEN1 and SYP122) are indispensable for the formation of papillae and encasements. Moreover, loss-of-function mutants were hampered in pre-invasive immunity towards a range of taxonomically distinct non-adapted filamentous pathogens, underlining the versatility and efficacy of this defense. Complementation studies using SYP12s from the early diverging land plant,Marchantia polymorpha, showed that the SYP12 clade immunity function has survived 470 My of independent evolution. These results suggest that ancestral land plants evolved the SYP12 clade to provide a broad and durable pre-invasive immunity to facilitate their life on land, and pave the way to a better understanding of how adapted pathogens overcome this ubiquitous plant defense strategy.