The plant stress hormone jasmonic acid evokes defensive responses in streptomycetes.

IMPORTANCE: Microorganisms that live on or inside plants can influence plant growth and health. Among the plant-associated bacteria, streptomycetes play an important role in defense against plant diseases, but the underlying mechanisms are not well understood. Here, we demonstrate that the plant hormones jasmonic acid (JA) and methyl jasmonate directly affect the life cycle of streptomycetes by modulating antibiotic synthesis and promoting faster development. Moreover, the plant hormones specifically stimulate the synthesis of the polyketide antibiotic actinorhodin in Streptomyces coelicolor. JA is then modified in the cell by amino acid conjugation, thereby quenching toxicity. Collectively, these results provide new insight into the impact of a key plant hormone on diverse phenotypic responses of streptomycetes.