An HR-induced tobacco peroxidase gene is responsive to spermine, but not to salicylate, methyl jasmonate, and ethephon

In Tobacco mosaic virus (TMV)-infected tobacco plants carrying the N resist ance gene, a hypersensitive reaction or response (HR) occurs to enclose the virus in the infected tissue. Although a contribution of peroxidases to th e resistance has been proposed, no evidence has been presented that tobacco peroxidase genes respond to HR, Here, we describe the HR-induced expressio n of a tobacco peroxidase gene (tpoxC1) whose induction kinetics were sligh tly different from those of acidic and basic tobacco pathogenesis-related ( PR) protein genes, Interestingly, tpoxC1 was insensitive to the inducers of PR genes such as salicylic acid, methyl jasmonate, and ethephon, Spermine activated tpoxC1 gene expression at a low level and both acidic and basic P R gene expression at a considerably higher level. These results indicate th at the induced expression of tpoxC1 is regulated differently from that of c lassical tobacco PR genes in the N gene-mediated self-defense system in tob acco plants.