Cloning and expression analysis of a viroid-induced peroxidase from tomato plants.

Differential hybridization was used to detect transcripts induced both by ethylene and by viroid infection in tomato plants. A cDNA clone encoding a putative peroxidase was isolated and characterized. DNA sequencing revealed high homology with a lignin-peroxidase from tobacco. Northern blot analysis showed specific induction of this peroxidase gene in viroid-infected plants. An increase in the level of mRNA accumulation is obtained by ethylene treatment, reinforcing the idea that ethylene is a mediator in the response of tomato plants to viroid infection.