Abstract
Proper mitochondrial function is crucial to plant growth and development. Inhibition of mitochondrial translation leads to mitochondrial proteotoxic stress, which triggers a protective transcriptional response that regulates nuclear gene expression, commonly referred to as the mitochondrial unfolded protein response (UPRmt). Although the UPRmt has been extensively studied in yeast and mammals, very little is known about the UPRmt in plants. Here, we show that mitochondrial translational stress inhibits plant growth and development by inducing jasmonic acid (JA) biosynthesis and signaling. The inhibitory effect of mitochondrial translational stress on plant growth was alleviated in the JA-signaling-defective mutants coi1-2, myc2, and myc234. Genetic analysis indicated that Arabidopsis mitochondrial ribosomal protein L1 (MRPL1), a key factor in the UPRmt, regulates plant growth in a CORONATINE-INSENSITIVE 1 (COI1)-dependent manner. Moreover, under mitochondrial translational stress, MYC2 shows direct binding to G boxes in the ETHYLENE RESPONSE FACTOR 109 (ERF109) promoter. The induction of ERF109 expression enhances hydrogen peroxide production, which acts as a feedback loop to inhibit root growth. In addition, mutation of MRPL1 increases JA accumulation, reduces plant growth, and enhances biotic stress resistance. Overall, our findings reveal that JA plays an important role in mediating retrograde signaling under mitochondrial translational stress to balance plant growth and defense.