Immune activation reprograms growth mRNA stability to shape plant growth-defense trade-offs

Immune activation enhances defense gene expression but often suppresses plant growth, creating a fundamental trade-off that limits durable resistance. While selective translation of defense mRNAs has been reported, how growth mRNAs are regulated after transcription during immune responses remains poorly understood. Here, using network-level analyses in Arabidopsis, we identify an RNA-binding protein-dependent mechanism that selectively destabilizes growth-related mRNAs upon immune activation. We show that polypyrimidine tract-binding protein 3 (PTBP3) recognizes a pyrimidine-rich RNA element, undergoes immune-induced condensation, and assembles an mRNA degradation hub that preferentially targets growth genes, including growth-regulating factors. Experimental disruption of this pathway-either by impairing PTBP3 function or by restoring growth gene expression-unexpectedly enhances disease resistance while improving growth resilience under immune stress. These findings reveal post-transcriptional control of growth mRNA stability as a regulatory layer shaping growth-defense balance and suggest a strategy for achieving stronger and safer plant immunity without constitutive defense activation.