CHARACTERIZATION OF A PATHOGEN-INDUCED POTATO CATALASE AND ITS SYSTEMIC EXPRESSION UPON NEMATODE AND BACTERIAL-INFECTION

We have isolated a cDNA encoding a catalase (Cat2St) by differential s creening of a cDNA library constructed from potato roots infected with the cyst nematode Globodera pallida. Expression analysis confirmed th e local induction of Cat2St and showed that it was highest at the adul t stage of the parasite. It also revealed that Cat2St was induced in u ninfected roots, stems, and leaves of infected plants. Localized and s ystemic induction of Cat2St was also observed upon root-knot nematode (Meloidogyne incognita) and root bacteria (Erwinia carotovora, Coryneb acterium sepedonicum) infections. Based on sequence and expression ana lysis, Cat2St was found to belong to the recently described class II o f dicotyledonous catalases, suggesting that these catalase isoforms co uld also be pathogen induced. Plant-parasitic nematodes are known to i nduce, in the roots of their hosts, highly metabolic feeding cells tha t function as nutritional sinks. Whereas the local induction of Cat2St is probably a consequence of an oxidative stress of metabolic nature, the systemic induction of Cat2St shows striking similarities with the induction of systemic acquired resistance (SAR) genes. The possible r ole of catalase in compatible plant-pathogen interactions is discussed .