Bacterial and fungal pathogens inflict major crop losses. The bacterium Xanthomonas oryzae pv. oryzae (Xoo), the causal agent for bacterial blight of rice, affects yield stability with losses up to 60% in the developing world. Three groups with complementary expertise have identified a fundamental mechanism for plant disease susceptibility involving Xoo-induced expression of sugar transporters known as SWEETs. SWEETs are involved in the translocation of sugars from photosynthetic leaves to roots, pollen, and seeds in uninfected plants. Xoo directly induces SWEET gene expression using TAL (transcription factor-like) effector proteins, which are injected from bacterium into leaf cells. The team has also shown that genetic alterations affecting TAL effector function through genomic editing of the target sequence in the host can be used to engineer pathogen resistance. The team hypothesizes that growth of the pathogen depends critically on nutrient supply from the host, and that Xoo specifically targets sugar release from leaf cells for supplying carbon and energy to the pathogen. They also hypothesize that this mechanism is relevant for other host/pathogen systems. This work lays the basis for engineering robust and broad disease resistance by targeting SWEETs encoded by a family of ~20 genes in rice and other crops. The results are expected to provide insight into durable and broad resistance and have global impacts on the environment and quality of life.
The insights gained from this project are relevant to engineering pathogen resistance in rice, but due to the fundamental nature of the mechanism the research may have impact in other crops. The project will provide training for high-school, undergraduate and graduate students, and postdocs with an emphasis on minorities at the interface between organismal interactions, cell biology and nutrition physiology. The work will enhance the educational environments at ISU, KSU, and the Carnegie Institution. The project will provide undergraduates with valuable experience in the latest tools of genetic analysis and engineering.
