DNAI1 and infection: Plants with reduced SA amounts due to the ectopic expression of the bacterial nahG gene (a SA-degrading salicylate hydroxylase) or dysfunction of the SA biosynthesis SID2/ICS1 gene (salicylic acid induction deficient 2/isochorismate synthase 1) exhibited reduced local and systemic resistance and were more susceptible to biotrophic pathogen infection, whereas the exogenous application of SA restored the resistance [2,3].