ERF transcription factor StPti5 is a regulator of endophyte community maintenance in potato

We have recently identified an ethylene response factor, StPti5, as a susceptibility factor that negatively regulates immune responses to diverse pathogens. Here, we investigated the role of StPti5 in the processes involved in the colonization of potato with beneficial organisms. RNA-seq showed that at the time of Bacillus subtilis biofilm establishment, immune responses in interacting roots were attenuated, and a complex transcriptional network was triggered, with ethylene signaling being a central module and StPti5 strongly induced. Interestingly, the response is intensified if plants are inoculated by two antagonistic B. subtilis strains. While StPti5 is not involved in the establishment of biofilm on roots, we show that bacterial abundance increases in shoots of StPti5-silenced plants. Remarkably, root colonization by the arbuscular mycorrhizal fungus Rhizophagus irregularis was also higher in the StPti5-silenced plants. To decipher the mechanistic basis of StPti5 function, we performed a DAP-seq experiment and showed that StRIN13, a regulator of plant immune signaling, is a direct target of StPti5. StPti5 is involved both in suppressing defense against harmful and limiting colonization by beneficial microbes. Such a mechanistic understanding of plant-microbe interaction paves the way for sustainable crop management.