|Bin Umer, Anwar|
Submitted to: National Fusarium Head Blight Forum Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/6/2012
Publication Date: 12/6/2012
Citation: Bin Umer, A., McLaughlin, J., McCormick, S.P., Tumer, N. 2012. Lipid transfer protein-mediated resistance to a trichothecene mycotoxin – Novel players in FHB resistance. National Fusarium Head Blight Forum Proceedings. Interpretive Summary:
Technical Abstract: Lipid transfer proteins are a class of basic cysteine rich proteins characterized by an eight cysteine motif backbone with intrinsic antimicrobial activities against bacterial and fungal pathogens. Previously, we identified two type IV nonspecific lipid transfer protein (nsLTP) genes (LTP4.4 and LTP4.5) from screening 250,000 activation-tagged Arabidopsis thaliana seeds. Overexpression of both genes enhanced resistance to trichothecin (Tcin). We set up yeast as a model system to investigate the mechanism by which the LTP4.4 and LT4.5 mediate resistance to trichothecenes. LTP4.4 and LTP4.5 expression conferred resistance to 2µM and 3µM Tcin in yeast. LTP4.4 provided a greater level of resistance than LTP4.5. In contrast, expression of a different nsLTP (LTP 1.1) did not provide resistance to trichothecin. Moreover, expression of LTP4.4 and LTP4.5 did not provide any resistance to other translation inhibitors, such as cycloheximide, anisomycin or chloramphenicol. These results suggest that resistance to trichothecenes is not a general response, but a feature unique to LTP4.4 and LTP4.5. Cell fractionation assays showed that while LTP4.4 remained largely in the cytosol, LTP4.5 was primarily associated with the membrane fractions, suggesting a difference in localization of the two nsLTPs. To explore the mechanism of nsLTP-mediated resistance to Tcin, we investigated the effects of Tcin on cytosolic and mitochondrial translation, two known targets of trichothecenes. Cytosolic translation was inhibited significantly (>65%), but mitochondrial translation was inhibited only minimally (<23%) by Tcin in cells overexpressing LTP4.4 and LTP4.5 relative to cells transformed with the vector alone. Reactive oxygen species (ROS) generation, an early time point event during trichothecene toxicity, was also alleviated in yeast overexpressing LTP4.4 and LTP4.5 with less than 2% of the cells generating any significant ROS at 2µM and 3µM Tcin. Taken together, these results suggest a likely role for mitochondria in nsLTP-mediated resistance to trichothecene toxicity.