Activation of Multiple Antiviral Defence Mechanisms by Salicylic Acid

SUMMARY The plant signal molecule salicylic acid (SA) can induce resistance to a wide range of pathogen types. In the case of viruses, SA can stimulate the inhibition of all three main stages in virus infection: replication, cell-to-cell movement and long-distance movement. Induction of resistance by SA appears to depend, in part, on downstream signalling via the mitochondrion. However, evidence has recently emerged that SA may stimulate a separate downstream pathway, leading to the induction of an additional mechanism of resistance based on RNA interference. In this review our aims are to document these recent advances and to suggest possible future avenues of research on SA-induced resistance to viruses.