New potato defense gene influences vesicle transport and recycling of defense proteins.
Together with partners from the Martin Luther University of Halle, IPB scientists have discovered a new defense-related gene of potato (Solanum tuberosum), which is increasingly expressed after Pep-13 infiltration of the plant. The identified gene StIPP codes for a membrane-localized inositol polyphosphate phosphatase. In vitro - as the Halle scientists showed - the recombinant enzyme catalyzes the dephosphorylation of phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2 or PIP2) in a very specific manner. Phosphatidylinositols are membrane lipids that modulate the formation of membrane vesicles as general transport vehicles for metabolites and cell proteins. In consequence of the plant immune response, PIP2 accumulates locally at the infection site and induces endocytosis and recycling processes of defense-related membrane proteins and activated PAMP receptors. Thus, acute defense reactions can be attenuated by this removal of the active players.
The Halle scientists assume that StIP-phosphatase acts as an antagonist in this scenario. In Phytophthora-infected potato plants, the researchers could show that in addition to PIP2, also StIPP accumulates in the extrahaustorial membrane, i.e. directly at the pathogen penetration site. StIPP-catalyzed dephosphorylation of PIP2 or a general modulation of the membrane lipid-driven vesicle trafficking could lead to a reduced recycling and a transient stabilization of the activated defense proteins in the plasma membrane. In this case, the acute phase of the defense reaction would be prolonged.