Location: Cereal Disease Lab2022 Annual Report
Objective 1: Investigate the biology of FHB infection, mycotoxin accumulation, and pathogenesis in the barley-Fusarium and related pathosystems. (NP303, C2, PS2A). This will include screening wheat lines for infection by Fusarium graminearum and accumulation of mycotoxins as well as detailed analysis of pathogen infection and process of toxin accumulation. • Sub-objective 1.A. Determine the protein content, spatial architecture, and functional significance of the toxin biosynthetic apparatus in Fusarium graminearum. • Sub-objective 1.B. Test for differentiation of the endoplasmic reticulum for specific primary and secondary terpenoid metabolite pathways upon trichothecene induction. Objective 2: Characterize pathogen diversity by studying natural fungal populations. • Sub-objective 2.A. Test for population subdivision among strains of F. graminearum isolated from native grasses versus those collected as pathogens on wheat or barley. Objective 3: Develop novel strategies for disease resistance in durum wheat and barley. • Sub-objective 3.A. Characterize the gene expression pattern changes in FHB resistant durum cultivars produced by removal of CG methylation. • Sub-objective 3.B. Characterize the genetic transmission of mutated loci and develop molecular markers for use in cultivar improvement.
Understanding how pathogens produce toxins and cause disease on different hosts can lead to improved management strategies for disease control. Specific approaches include: 1) Protein tagging, advanced microscopy, and protein-protein interaction techniques will be used to characterize multi-enzyme complexes involved in toxin biosynthesis and fungal pathogenesis; 2) FHB levels, strain diversity, and the nature of associated fungal communities, will be monitored by population genetic and metagenomic approaches improving the ability to forecast the economic impact and the design of effective management strategies; and 3) Novel sources of FHB resistance and mycotoxin tolerance will be developed and characterized for crop plants.
This is the first report for this new project which began in March 2022 and continues research from the previous project, 5062-21220-022-000D, "Fusarium Head Blight of Cereals: Pathogen Biology, Associated Phytobiome, and Host Resistance". Objective 1: Investigate the biology of FHB infection, mycotoxin accumulation, and pathogenesis in the barley-Fusarium and related pathosystems. We have generated strains with fluorescent protein (FP) fusions in Tri11, Cpr1, Cpr2, Sec22, Clm1, Clm2, Erg1, Erg11, and Erg25. These proteins are involved in trichothecene toxin biosynthesis (Tri11), redox metabolism (Cpr1, Cpr2), vesicle trafficking (Sec22), culmorin toxin biosynthesis (Clm1, Clm2), and ergosterol biosynthesis (Erg1, Erg11, Erg25). These strains have been crossed with strains FP-tagged with other proteins (Tri4, Hmr1) known to localize to toxisomes to perform co-localization and fluorescence resonance energy transfer analyses to test for physical proximity and protein-protein interactions during toxin-inducing conditions. We have also generated strains with mutant versions of the Tri5 protein that result in mislocalization (peroxisome- or ER-tethered), loss of predicted palmitoylation (altered membrane localization), or loss of enzymatic activity. Objective 2: Characterize pathogen diversity by studying natural fungal populations. Travel restrictions due to the impact of Covid-19 prevented progress in collecting samples in large numbers from across the United States. A new SY was hired in June 2022 and plans to take collections of wheat fields and native plants later this year. Objective 3: Develop novel strategies for disease resistance in durum wheat and barley. We have collected additional RNA samples from the remaining 3 durum mutant lines and their parents and controls at various conditions to confirm our initial findings from previous work indicating 25 candidate genes. The samples are being sequenced and analysis is forthcoming. We have also generated hybrids between all five durum mutant lines and two popular durum wheat cultivars. These lines will be crossed in the fall greenhouse season to generated BC1F1 lines and then advanced by selfing to generate a nested association mapping populations for both introgression of resistant genes and further genetic characterization of resistant loci.