The infection of plants with the gram-negative bacteria Pseudomonas syringae, the oomycetes Phytophthora infestans and Phytophthora parasitica and the necrotrophic ascomycetes Botrytis cinerea and Sclerotinia sclerotiorum elevated the expression of PGDH1, PGDH2 and PSAT1 of around two to seven-fold. Here, PSAT1 is linked to infection.