Signaling of systemic acquired resistance in tobacco depends on ethylene perception.

The hypersensitive interaction between Tobacco mosaic virus (TMV) and tobacco results in accumulation of salicylic acid (SA), defense gene expression, and development of systemic acquired resistance (SAR) in uninfected leaves. The plant hormones SA and ethylene have been implicated in SAR. From a study with ethylene-insensitive (Tetr) tobacco, we concluded that ethylene perception is required to generate the systemic signal molecules in TMV-infected leaves that trigger SA accumulation, defense gene expression, and SAR development in uninfected leaves. Ethylene perception was not required for the responses of the plant to the systemic signal that leads to SAR development.