Identification of amino acid residues of the Fusarium verticillioides endo-polygalacturonase required to escape the inhibition by host plant PGIP.

Endopolygalacturonases (Endo-PGs) play an important role during fungal infection since they depolymerize the pectin component of plant cell wall. Most plant have evolved defence mechanisms to contrast the action of endo-PGs. A direct mechanism is the interaction with plant cell wall polygalacturonase-inhibiting proteins (PGIPs) that block the polygalacturonase activity. However, fungal pathogens can elude the inhibition by plant PGIP producing PGs refractory to inhibition. F. verticillioides endo-PG is unaffected by host PGIPs (asparagus and leek) as well as by Phaseolus vulgaris PGIP, that is the most efficient PGIP so far characterized. Recently, we have identified a specific amino acid residues of the PG responsible of the lack of recognition by bean PGIP. Now we have mutated few amino acids of the F. verticillioides endo-PG which allow the recognition by host PGIP. This finding highlights the structural features of the enzyme to escape PGIP inhibition. Moreover, this modified PG could be used to replace the native PG of F. verticillioides in order to better clarify the role of constitutive PGIP in plant defence.