Firstly, the expression of SlSAHH1 was significantly downregulated and accordingly, the SAHH activity was also decreased in both the SlSAHHs-co-silenced and non-silenced plants after infection by Pst DC3000, implying that suppression of the SAHH activity may be required for effectively activation of defense response upon infection of Pst DC3000. This evidence concerns the gene AHCY and infection.