Ricerc@Sapienza

Recognition at the plasma membrane of danger signals (elicitors) belonging to the classes of the microbe/pathogen- and damage-associated molecular patterns is a key event in pathogen sensing by plants and is associated with a rapid activation of immune responses. Different cellular compartments, including plasma membrane, chloroplasts, nuclei and mitochondria, are involved in the immune cellular program. However, how pathogen sensing is transmitted throughout the cell remains largely to be uncovered.

Aphids are among the most destructive pests in agriculture, causing direct damage to crops by feeding on phloem, as well as indirect losses by transmitting more than half of all described plant viruses. During feeding aphids secrete effector proteins into their hosts to manipulate cellular processes and promote infestation. Aphids are largely controlled by pesticides that are environmentally damaging and are being withdrawn from the market.

In order to cause a disease, pathogens need to break the plant cell wall and to this purpose they secrete degrading enzymes towards various cell wall components. Several oligosaccharides released during pathogenesis, such as the Oligogalacturonides (OGs) and Cellodextrins (CDs) upon the breakdown of the homogalacturonan and cellulose respectively, act as Damage-Associated Molecular Patterns (DAMPs) and activate immunity.

Pectic homogalacturonan (HG) is one of the main constituents of plant cell walls. When processed to low degrees of esterification, HG can form complexes with divalent calcium ions. These macromolecular structures (also called egg boxes) play an important role in determining cell wall biomechanics and in mediating cell-to-cell adhesion. Current immunological methods enable only steady-state detection of egg box formation in situ. Here we present a tool for efficient real-time visualisation of available sites for HG crosslinking within cell wall microdomains.