Constitutive activation of plant immunity is detrimental to plant growth and development. Here, we uncover the role of a long non-coding RNA (lncRNA) in fine-tuning the balance of plant immunity and growth. We find that a lncRNA termed salicylic acid biogenesis controller 1 (SABC1) suppresses immunity and promotes growth in healthy plants. SABC1 recruits the polycomb repressive complex 2 to its neighboring gene NAC3, which encodes a NAC transcription factor, to decrease NAC3 transcription via H3K27me3. NAC3 activates the transcription of isochorismate synthase 1 (ICS1), a key enzyme catalyzing salicylic acid (SA) biosynthesis. SABC1 thus represses SA production and plant immunity via decreasing NAC3 and ICS1 transcriptions. Upon pathogen infection, SABC1 is downregulated to derepress plant resistance to bacteria and viruses. Together, our findings reveal lncRNA SABC1 as a molecular switch in balancing plant defense and growth by modulating SA biosynthesis.

植物免疫的组成性激活不利于植物的生长发育。在这里，我们揭示了长链非编码 RNA (lncRNA) 在微调植物免疫和生长平衡中的作用。我们发现一种称为水杨酸生物发生控制器 1 ( SABC1 ) 的 lncRNA 抑制免疫并促进健康植物的生长。SABC1将多梳抑制复合物 2 募集到其邻近基因NAC3中，该基因编码 NAC 转录因子，以通过 H3K27me3减少NAC3转录。NAC3激活异分支酸合酶 1 ( ICS1 ) 的转录，ICS1 是催化水杨酸 (SA) 生物合成的关键酶。因此， SABC1通过减少NAC3和ICS1转录来抑制 SA 的产生和植物免疫。在病原体感染后，SABC1被下调以抑制植物对细菌和病毒的抵抗力。总之，我们的研究结果揭示了 lncRNA SABC1作为通过调节 SA 生物合成来平衡植物防御和生长的分子开关。