Team:WashU StLouis/Description

What are we doing?

For the past two decades, wheat stem rust fungus caused by Puccinia graminis f. sp. tritici (Pgt) has spread across the world, severely damaging the world’s food supply. Conventionally, farmers look for physical structures called pustules to check for the presence of Pgt, and therefore must wait 7 to 15 days for the physical symptoms to form. By designing an early detection mechanism, farmers will be able to apply fungicide and treat their crops before the disease progresses. In addition, damage from the fungus is more severe when infection occurs early in plant development, making early detection crucial in crop efficacy.

In order to test for the presence of Pgt spores, we propose a two step mechanism: detecting and profiling.

The detection aspect of our project will produce a signal alerting farmers of the presence of Pgt spores, regardless of virulence by detecting ribitol. By transforming E. coli DH5α, which does not naturally respond to ribitol, with a plasmid carrying a promoter induced by ribitol upstream of a fluorescent protein, we aim to detect the presence ribitol, and therefore the presence Pgt.

The profiling component of our project aims to distinguish the virulence of the race of Pgt present.

The Sr35 resistance gene from wheat crops can be expressed in Saccharomyces cerevisiae EBY100 and engineered to produce a signal when the resistance factors recognize the corresponding avirulence factor, AvrSr35. If this recognition occurs, it shows that any plants with Sr35 will be immune to infection from the race of Pgt present.

Coupling with the two mechanisms together, we are able to discern for both the presence of Pgt as well as if the strain is virulent to the crops. If a signal is produced in the detection step but not profiling, the race of Pgt is virulent to Sr35.