The results of our transcription analysis further revealed that different layers of the host's pathogen defense were not activated: Neither R-genes (RPPA), PR-genes (Chitinase and Prot-206), genes involved in HR (Metacaspase) or signal transduction through SA (EDS-5) nor ROS scavenger genes (APX, CAT, SOD, GST) showed enhanced transcription after infection of Z. marina with L. zosterae. This evidence concerns the gene ROS1 and infection.