RESISTANCE GENE N-MEDIATED DE-NOVO SYNTHESIS AND ACTIVATION OF A TOBACCO MITOGEN-ACTIVATED PROTEIN-KINASE BY TOBACCO MOSAIC-VIRUS INFECTION

Salicylic acid-induced protein kinase (SIPK) and wounding-induced prot ein kinase (WIPK), two distinct members of the mitogen-activated prote in (MAP) kinase family, are activated in tobacco resisting infection b y tobacco mosaic virus (TMV). WIPK activation by TMV depends on the di sease-resistance gene N because infection of susceptible tobacco not c arrying the N gene failed to activate WIPK. Activation of WIPK require d not only posttranslational phosphorylation but also a preceding rise in its mRNA and de novo synthesis of WIPK protein. The induction by T MV of WIPK mRNA and protein also occurred systemically. Its activation at the mRNA, protein, and enzyme levels was independent of salicylic acid. The regulation of WIPK at multiple levels by an N gene-mediated signal(s) suggests that this MAP kinase may be an important component upstream of salicylic acid in the signal-transduction pathway(s) leadi ng to local and systemic resistance to TMV.