CDK8 coordinates jasmonate-induced immunity with sulfur-responsive defense in <i>Arabidopsis</i>

Abstract

Plant immunity draws heavily on carbon-, nitrogen-, and sulfur-based precursors for the deployment of specialized defense compounds. The jasmonate signaling pathway promotes expression of metabolically costly defenses, often at the expense of growth. How plants coordinate growth–defense tradeoffs with changes in nutrient availability remains poorly understood. Here, we identify CYCLIN-DEPENDENT KINASE 8 (CDK8) as a transcriptional regulator that restrains growth and reduces seed yield under conditions of heightened jasmonate signaling in Arabidopsis thaliana and further show that CDK8 shapes immune responses according to sulfur availability. Transcript and metabolite profiling showed that CDK8 amplifies jasmonate-triggered immunity, including robust accumulation of glucosinolates, camalexin, and sulfur-rich defensin peptides under sulfur-replete conditions. Strikingly, sulfur limitation triggered a CDK8-dependent transcriptional switch that suppressed defensins and glucosinolates while coordinately inducing camalexin, a defense metabolite requiring substantially lower sulfur investment. These findings establish CDK8 as a regulator that integrates jasmonate signaling with sulfur nutritional status to shape the composition of plant immune responses.