Plants have evolved complex signaling pathways to coordinate responses to developmental and environmental information.  The oxylipin pathway is one pivotal lipid-based signaling network that determines the plant’s ability to adapt to various stimuli.  Much of the research on oxylipins to date has focused on the branch pathway involving jasmonates.  The parallel, stress-inducible HYDROPEROXIDE LYASE (HPL) branch pathway remains poorly characterized.  The HPL enzyme catalyzes the cleavage of fatty acid hydroperoxides into aldehydes and oxoacids.  These volatile metabolites are postulated to play key signaling roles within and between plants, as well as in plant-insect interactions. We are interested to dissect: (a) the signal transduction machinery responsible for stress-inducible transcriptional regulation of the HPL gene, and (b) the signaling role of the derived HPL-pathway metabolites in mediating intra- and inter-plant stress responses.  We have already established that the expression of HPL and its cognate pathway metabolites are stress-induced.  To begin to identify regulatory components in this signaling network, we generated an HPL::luciferase(LUC)-transgenic line.  By using these plants in an imaging-based genetic screen, we identified mutants that express LUC constitutively, suggesting constitutive activation or derepression of the HPL promoter.  To characterize the signaling role of the aldehydes in stress responses, we have generated a genetic tool box of lines that produce a range of aldehyde levels, thus providing us with an experimental system to define the link between endogenous aldehyde levels and target-gene expression.

Specifically our objectives are:
1- The molecular components responsible for stress-inducible transcriptional regulation of HPL, using a range of molecular-genetic and biochemical approaches.
2- The transcriptional regulatory networks that mediate the aldehyde-induced gene expression program.  Here, we have employed microarray-based expression profiling of hpl mutants and HPL over-expressors, followed by quantitative real-time RT-PCR analysis of a subset of genes in order to define those genes that are primary targets of the HPL signaling pathway.
3- The role of HPL-pathway metabolites in mediating inter-plant stress-responses, by expression profiling in WT neighbors of hpl mutants and HPL overexpressors.