Long lasting impact of chito-oligosaccharide application on strigolactone biosynthesis and fungal accommodation promotes arbuscular mycorrhiza in Medicago truncatula

Arbuscular mycorrhizal (AM) association is an ancient symbiosis between plant roots and soil-borne fungi, supporting mineral nutrition in most crop plants. Symbiosis establishment is preceded by the exchange of chemical signals between partners: root-exuded strigolactones and fungal-released short chain chitooligosaccharides (CO) that activate symbiotic responses and promote AM development. We here combined molecular, cellular and biochemical approaches to demonstrate that CO treatment changed root gene expression pattern and led to a global advancement in both early (strigolactone biosynthesis, fungal accommodation) and late (arbuscule senescence) symbiotic responses, providing a novel and exhaustive view of the molecular bases underpinning CO promotion of AM development.