Mechanisms of transcriptional regulation by salicylic acid receptors.

Salicylic acid activates Arabidopsis defence transcription by enabling NPR1 to bind MED15A and by disrupting NPR3/NPR4 repression, reducing H3K27 trimethylation and increasing histone acetylation.

• Why it matters: The link between SA perception by NPR receptors and how defence genes switch on remains unclear, limiting rational design of SA-based agrochemicals and crop-resistance engineering.
• What they did: The study mapped SA-dependent interactions, showing SA induces direct NPR1–MED15A binding; structural/functional tests indicated this binding is essential for NPR1-driven activation. It also found SA disrupts NPR3/NPR4 and NIM1-interacting 1–TOPLESS–PRC2 repression, lowering H3K27 trimethylation and raising histone acetylation.
• The result: SA-mediated defence gene activation is explained through both transcriptional activation via NPR1–MED15A and repression relief via NPR3/NPR4–PRC2, providing a mechanistic basis for engineering SA signalling and designing SA analogues.

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