The transcriptional landscape of Arabidopsis thaliana pattern-triggered immunity

Plants tailor their metabolism to environmental conditions, in part through recognition of a wide array of self and non-self molecules. In particular, the perception of microbial or plant-derived molecular patterns by cell surface-localized pattern recognition receptors (PRRs) induces pattern-triggered immunity, which includes massive transcriptional reprogramming(1). While an increasing number of plant PRRs and corresponding ligands are known, whether plants tune their immune outputs to patterns of different biological origins or of different biochemical nature remains mostly unclear. Here, we performed a detailed transcriptomic analysis in an early time-series focused to study rapid signaling transcriptional outputs induced by well-characterized patterns in the model plant Arabidopsis thaliana. This revealed that the transcriptional response to diverse patterns – independent of their origin, biochemical nature, or type of PRR – is remarkably congruent. Moreover, many of the genes most rapidly and commonly up-regulated by patterns are also induced by abiotic stresses, suggesting that the early transcriptional response to patterns is part of the plant general stress response (GSR). As such, plant cells’ response is in the first instance mostly to danger. Notably, genetic impairment of the GSR reduces pattern-induced anti-bacterial immunity, confirming the biological relevance of this initial danger response. Importantly, the definition of a small subset of ‘core immunity response’ genes common and specific to pattern response revealed the function of previously uncharacterized GLUTAMATE RECEPTOR-LIKE (GLR) calcium-permeable channels in immunity. This study thus illustrates general and unique properties of early immune transcriptional reprogramming that uncovered important components of plant immunity.