The chromatin regulator MOM1 is a negative component of the defense priming induced by AZA, BABA and PIP.

In plants, the establishment of broad and long-lasting immunity is based on programs that control systemic resistance and immunological memory or "priming". Despite not showing activated defenses, a primed plant induces a more efficient response to recurrent infections. Priming might involve chromatin modifications that allow a faster/stronger activation of defense genes. The chromatin regulator "" (MOM1) has been recently suggested as a priming factor affecting the expression of immune receptor genes. Here, we show that mutants exacerbate the root growth inhibition response triggered by the key defense priming inducers azelaic acid (AZA), β-aminobutyric acid (BABA) and pipecolic acid (PIP). Conversely, mutants complemented with a minimal version of MOM1 ( plants) are insensitive. Moreover, is unable to induce systemic resistance against sp. in response to these inducers. Importantly, AZA, BABA and PIP treatments reduce the expression, but not transcript levels, in systemic tissues. Consistently, several MOM1-regulated immune receptor genes are upregulated during the activation of systemic resistance in WT plants, while this effect is not observed in . Taken together, our results position MOM1 as a chromatin factor that negatively regulates the defense priming induced by AZA, BABA and PIP.