Hydroxyzimtsäureamide als Abwehrstoffe gegen Phytophthora infestans in Arabidopsis thaliana und Solanum tuberosum

Abstract

Phytophthora infestans ist der Erreger der Kraut- und Knollenfäule in Kartoffel (Solanum tuberosum). Nach Kontakt mit P. infestans sind in Arabidopsis mehr als 700 Gene aktiviert. Zwei dieser Gene sind AtACT1 und AtMATE. AtACT1 katalysiert die Kondensation des biogenen Amin Agmatin mit dem Hydroxycinnamoyl-CoA-Ester p-Cumaroyl-CoA zu dem Hydroxyzimtsäureamid p-Cumaroylagmatin. AtMATE bewerkstelligt den Transport von p-Cumaroylagmatin in den Apoplasten. Erst die Expression beider Gene, AtACT1 und AtMATE führt zu einem Transport des durch AtACT1 synthetisierten p-Cumaroylagmatins nach außen. Dies führt zu einer gesteigerten Resistenz der transgenen AtACT1-AtMATE exprimierenden Pflanzen gegenüber Kontrollpflanzen und zu einem morphologischen Phänotyp.

Phytophthora infestans is the causal agent of late blight, the most devastating potato disease. The major secondary metabolites accumulating in response to pathogen infection in potato are hydroxycinnamic acid amides (HCAAs). In addition to their function as antimicrobial compounds, HCAAs are required for the reinforcement of the plant cell wall. The model plant Arabidopsis thaliana is also producing HCAAs after pathogen challenge, but the potato enzymes catalyzing the synthesis of HCAAs are different from those of A. thaliana. A gene was identified, which encodes an agmatine N4-coumaroyl transferase and in addition a highly coexpressed MATE (multidrug and toxic compound extrusion) transporter which is required for export of the HCAA p-coumaroylagmatine in A. thaliana. LC-MS studies revealed that there is less p-coumaroylagmatine at the surface of potato leaves in contrast to A. thaliana leaves. The aim was to produce potato plants with altered HCAA profiles to study the influence of these compounds on the interaction of potato and P. infestans.