William Ricci

Investigating the role of salicylic acid-binding proteins in photo-oxidative stress

Project Summary

Salicylic acid (SA) is a small, plant-derived phenolic molecule that is an essential regulator of plant defense-related signal transduction against pathogens and abiotic stress.  Physical interactions between SA and endogenous targets are critical for SA-dependent signaling.  However, the effects that SA-binding targets have on signal transduction are largely unknown.

Recently, two thimet metalloendopeptidases (TOP1 and TOP2), were found to directly bind SA.  These proteins are of interest because they are required for fully functional effector-triggered immunity and they play potentially important roles in the mitigation of cellular oxidative stress.  top2 mutants were found to exhibit hypersensitivity to an exogenous inducer of photo-oxidative stress.  We sought to gain insight into how TOP2’s oligopeptidase activity assists cells in recovery from overproduction of reactive oxygen species (ROS) and how this relates to TOP1 and TOP2’s capacity for SA-binding.

We utilized split luciferase complementation to investigate the nature of TOP1 and TOP2 protein-protein interactions under the influence of various concentrations of SA.  Additionally, we searched for differential conditional phenotypes (induced by photo-oxidative stress) by assessing photosynthetic efficiency (via chlorophyll fluorescence), cell death rates (via ion leakage from leaf disks), and the spread of reactive oxygen species in leaves (via 3,3′-Diaminobenzidine staining).  We found that various concentrations of exogenous SA modulate TOP1 and TOP2 protein-protein interactions and that application of an exogenous photo-oxidative stress inducer modulates TOP2 expression. Hopefully our test results will clarify many details of the SA-ROS positive feedback loop which remain elusive.  .

My Experience

The Plant Genome Research Program has confirmed my interest in pursuing scientific research.  The one-on-one student-mentor nature of the program gave me freedom to independently develop and troubleshoot experimental assays.  As a consequence, it has introduced me to the difficulties, as well as the triumphs, of scientific research.  Additionally, the program  offered valuable insight into the life of research scientists as a profession.  I have learned that science can be highly social and collaborative and that one’s success relies heavily on interpersonal communication.  This experience has secured my decision to pursue a career in science.  I enjoyed the Cornell campus, Ithaca, the town and the parks. The fury of the waterfalls, the tranquility of the arboretum, and of the periodic chiming of McGraw tower made Ithaca an exceedingly pleasant place to spend the summer.