Genes controlling expression of defense responses in Arabidopsis - 2001 status

In the past two years, the focus of studies of the genes controlling expres sion of defense responses in Arabidopsis has shifted from the identificatio n of mutants to gene isolation and the ordering of genes within branches of the signal transduction networks. It is now clear that gene-for-gene resis tance can be mediated through at least three genetically distinguishable pa thways, Additional genes affecting salicylic-acid-dependent signaling have been identified, and double-mutant analyses have begun to reveal the order in which they act. Genes required for jasmonic-acid-dependent signaling and for induced systemic resistance have also been identified.