| Upon wounding in the leaves of Solanum lycopersicum, the 18 amino acid signaling peptide systemin is processed from its precursor and interacts with a membrane bound receptor. This initiates a signal transduction pathway involving a MAPKinase cascade, leading to the local and systemic synthesis of defense compounds that act in the insect midgut to interfere with digestion. Previous work has shown that MPK1, MPK2, and MPK3 are involved in this pathway, but the upstream MPKinase Kinases (MKK) involved in transduction of the systemin signal have not been characterized. However MKK2 and MKK4 have been shown to activate MPK1, MPK2 and MPK3 in response to the plant pathogen Pseudomonas syringae, raising the possibility that they may also be involved in transduction of the systemin signal. My research was aimed at investigating the potential role these MKKs in transduction of the systemin signal, using virus-induced gene silencing as a method to reduce their expression. In addition I have also investigated an uncharacterized receptor-like kinase that was identified based on its homology to Brassinosteroid Insensitive 1, a receptor-like kinase that binds systemin but is unable to respond to it. |
