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N 6-methyladenosine (m6A) is a common epitranscriptional mRNA modification in eukaryotes. Thirteen putative m6A readers, mostly annotated as EVOLUTIONARILY CONSERVED C-TERMINAL REGION (ECT) proteins, have been identified in Arabidopsis (Arabidopsis thaliana), but few have been characterized. Here, we show that the Arabidopsis m6A reader ECT1 modulates salicylic acid (SA)-mediated plant stress responses. ECT1 undergoes liquid-liquid phase separation in vitro, and its N-terminal prion-like domain is critical for forming in vivo cytosolic biomolecular condensates in response to SA or bacterial pathogens. Fluorescence-activated particle sorting coupled with quantitative PCR analyses unveiled that ECT1 sequesters SA-induced m6A modification-prone mRNAs through its conserved aromatic cage to facilitate their decay in cytosolic condensates, thereby dampening SA-mediated stress responses. Consistent with this finding, ECT1 overexpression promotes bacterial multiplication in plants. Collectively, our findings unequivocally link ECT1-associated cytosolic condensates to SA-dependent plant stress responses, advancing the current understanding of m6A readers and the SA signaling network., Competing Interests: Conflict of interest statement. None declared., (© The Author(s) 2023. Published by Oxford University Press on behalf of American Society of Plant Biologists. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

N6-methyladenosine (m6A) is a common epitranscriptional mRNA modification in eukaryotes. Thirteen putative m6A readers, mostly annotated as EVOLUTIONARILY CONSERVED C-TERMINAL REGION (ECT) proteins, have been identified in Arabidopsis (Arabidopsis thaliana), but few have been characterized. Here, we show that the Arabidopsis m6A reader ECT1 modulates salicylic acid (SA)–mediated plant stress responses. ECT1 undergoes liquid–liquid phase separation in vitro, and its N-terminal prion-like domain is critical for forming in vivo cytosolic biomolecular condensates in response to SA or bacterial pathogens. Fluorescence-activated particle sorting coupled with quantitative PCR analyses unveiled that ECT1 sequesters SA-induced m6A modification-prone mRNAs through its conserved aromatic cage to facilitate their decay in cytosolic condensates, thereby dampening SA-mediated stress responses. Consistent with this finding, ECT1 overexpression promotes bacterial multiplication in plants. Collectively, our findings unequivocally link ECT1-associated cytosolic condensates to SA-dependent plant stress responses, advancing the current understanding of m6A readers and the SA signaling network. The m6A reader EVOLUTIONARILY CONSERVED C-TERMINAL REGION 1 modulates salicylic acid–dependent plant stress responses, such as growth inhibition and cell death, in cytosolic biomolecular condensates. [ABSTRACT FROM AUTHOR]