Ricerc@Sapienza

This project aims at elucidating the role and dynamics of bioactive oligosaccharides derived from the plant extracellular matrix [ECM, also indicated as cell wall (CW)], acting as regulatory molecules in both immunity and development. A main focus of the project is on oligogalacturonides (OGs), oligosaccharides deriving from the fragmentation of the homogalacturonan (HGA), a main component of pectin in the CW, that act as damage-associated molecular patterns (DAMPs). In animals, hyaluronan, also a linear negatively charged polysaccharide that can be considered the vertebrate counterpart of HGA, is a molecular powerhouse with critical roles in homeostasis and disease onset, progression, and recovery, and its fragments are potent inducers of immunity and therefore classical DAMPs. Although OGs are the first DAMPs ever discovered, much is unknown about their biology due to the complexity of their mediated signaling and the difficulty of isolating mutants defective in specific or general responses to OGs. By exploiting unique tools and expertise developed in many years, this project aims at proving the hypothesis that OGs, besides acting as DAMPs when present at high levels in stress conditions, also play a role in development when they are released at low levels during the physiological cell wall remodeling. Moreover, it aims at dissecting the pathways involved in the role of OGs as mediator of the growth-defense trade-off and elucidating their possible interplay with fragments derived from another important cell wall component, cellulose, that are described as a novel class of DAMPs. Finally, the project aims at demonstrating that inactivation of CW fragments accomplished by newly discovered specific oxidases belonging to the complex berberine bridge enzyme-like family is a homeostatic mechanism that prevents hyper-accumulation of OGs and hyper-immunity. Disentangling the mechanisms of CW--mediated signaling may lead to novel strategies of crop protection.