A lncRNA fine-tunes salicylic acid biosynthesis to balance plant immunity and growth

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. [Display omitted] •lncRNA SABC1 suppresses immunity and promotes growth in healthy plants•SABC1 represses the transcription factor NAC3 in cis•NAC3 activates expression of the SA biosynthesis enzyme ICS1•Pathogen infection decreases SABC1 expression leading to derepression of immunity Liu et al. discover a lncRNA in Arabidopsis as a key regulator balancing immunity and growth. The lncRNA fine-tunes salicylic acid (SA) biosynthesis through regulating the expression of a neighboring transcription factor that controls SA biosynthesis. Expression of the lncRNA decreases upon pathogen infection, leading to derepression of immunity.