PHOTOSENSITIZING TETRAPYRROLES INDUCE ANTI-OXIDATIVE AND PATHOGEN DEFENCE RESPONSES IN PLANTS
H-P MOCK, U KEETMAN and B GRIMM
Institut für Pflanzengenetik und Kulturpflanzenforschung, Corrensstrasse 3, D-06466 Gatersleben, Germany
Background and objectives
Results and conclusions
In parallel to the induction of anti-oxidative defence reactions, accumulation of tetrapyrroles induces cellular responses normally associated with pathogen defence. UROD and CPO antisense plants accumulate the highly fluorescent coumarin scopolin, a compound which is also formed after TMV infection of tobacco. In addition, plants with leaf lesions display increased pathogenesis-related protein expression and higher levels of free and conjugated salicylic acid. Plants with the necrotic phenotype of several transgenic lines show increased resistance to TMV, relative to wild-type controls or transformants without leaf lesions. Our results demonstrate that deregulation of tetrapyrrole biosynthesis can induce a set of defence responses resembling the hypersensitive reaction observed after pathogen attack. We hypothesize that reactive oxygen species derived from excessive tetrapyrroles interfere with signalling events inducing pathogen defence responses. Experiments are currently being performed to dissect the molecular events leading to anti-oxidative and pathogen defence responses. In conclusion, our model system offers the future possibility to improve pathogen defence responses in plants by genetically modifying the tetrapyrrole biosynthetic pathway.