The molecular mechanisms underlying trichothecene toxicity in plants are poorly understood and this places limits on our ability to engineer resistance to trichothecenes and ultimately Fusarium graminearum (F.g.).  Previously we found that deoxynivalenol (DON) induces the chloroplast unfolded protein response (cpUPR) in Chlamydomonas and that mutants that play a role in the cpUPR were identified as highly sensitive to trichothecenes.  In addition, several other mutants in proteins which function to resolve proteotoxic stress within the chloroplast were found to have substantially reduced fitness compared to the wild type.  We have since identified that DON rapidly induces the VESICLE-INDUCING PROTEIN IN PLASTIDS 2 (VIPP2) gene which plays a role in managing chloroplast membrane stress.  This gene was previously found to be upregulated under high light and oxidative stress conditions.  Induction of VIPP2 is part of a retrograde stress response which upregulates small heat shock proteins (sHSPs) like HSP22E/F, sHSPs which function to return the chloroplast to homeostasis following periods of stress.  If trichothecenes similarly target higher plant chloroplasts, we predict that the resulting chloroplast stress would contribute to F.g. virulence.  To begin this investigation, we are testing the impact of trichothecenes on VIPP2 orthologs in Arabidopsis, wheat, and barley.  The goal is to identify if chloroplasts from higher plants are impacted by trichothecenes, measure the magnitude of impact, and understand the potential role of the chloroplast protein quality control (cpPQC) system in response to trichothecene-induced damage.  This study may provide unique methods to increase resistance to trichothecenes and F.g.

ACKNOWLEDGEMENT

We thank Silvia Ramundo at the Vienna BioCenter (Austria) for providing the mars1 and MARS1 overexpression mutants in addition to other resources used in this research.