Identification of potential biomarkers in astragali radix for resistance to root rot caused by Fusarium solani. F. GAO, H. D. YUE, X. M. QIN AND A. XUE. Institute of Applied Chemistry, Shanxi University, Taiyuan 030006, China; (F.G., A.X.) Ottawa Research and Development Centre, Agriculture and Agri-Food Canada, 960 Carling Avenue, Ottawa, ON K1A 0C6, Canada; and (H.D.Y., X.M.Q.) Modern Research Center for Traditional Chinese Medicine, Shanxi University, Taiyuan 030006, China
Root rot, caused by Fusarium salani (FS), is a destructive disease of astragali radix (Astragalus membranaceus), a traditional Chinese medicine used in Asia for its immunostimulant, hepatoprotective, tonic, diuretic, antidiabetic properties. Breeding for disease resistance has been considered as the best option for managing astragali radix root rot. Several resistance-related (RR) metabolites and their corresponding genes of synthesis have been identified. Our study focused on a time series profiling of metabolome in astragali radix during infection and disease development, using the untargeted 1H nuclear magnetic resonance (NMR)-based metabolomics method. Of the 24 metabolites examined, 13 metabolites were quantitatively altered after plants were inoculated with FS at 7, 14 and 21 days, compared with non-inoculated plants served as the control. Seven of the 13 altered metabolites showed a significant correlation with the disease severity and are considered potential biomarkers. Four of the seven metabolites including malic acid, phenylalanine, fructose and sucrose were negatively correlated with disease severity and may be used as potential RR biomarkers; while valine, arginine and glutamine were positively correlated with disease severity and may be used as susceptible-related (SR) biomarkers. Among the four potential RR biomarkers, only malic acid inhibited fungal growth, fructose and sucrose had no effect, while phenylalanine along with the three SR related metabolites enhanced fungal growth. The results suggest that not all RR metabolites inhibit fungal growth and they may contribute to reducing the fungal pathogenicity or increasing plant defence in the astragali radix–FS pathogenesis.
A reminiscence of evolutionary hourglass: the pattern of ergot alkaloid gene divergence in Claviceps purpurea. M. LIU, W. FINDLAY, P. SHOUKOUHI, K. DADEJ, H. D. T. NGUYEN, J. G. MENZIES AND K. A. SEIFERT. Biodiversity (Mycology and Microbiology), Ottawa Research and Development Centre, Agriculture and Agri-Food Canada (AAFC), Ottawa, ON K1A 0C6, Canada; and (J.G.M.) Morden Research and Development Centre, AAFC, Morden, MB R6M 1Y5, Canada
The pattern of genetic divergence during embryo development in animals and plants was interpreted as following an early conservation model until an hourglass model was proposed in the 1990s, i.e. diverged early and late stages connected by a conserved middle stage. The debate over which model holds true is inconclusive, while comparative genomics provided evidence to support the hourglass model at the molecular level. According to the biogenetic hypothesis, ontogeny recapitulates phylogeny. It is possible that these models exist in other evolutionary processes, such as metabolic biosynthesis pathways. Mycotoxins produced by ergot fungi have significant detrimental and beneficial impacts on the economy, ecology and health, leading to the in-depth study and clarification of the biosynthesis pathway, and a good system to test these hypotheses. In Claviceps purpurea and close relatives, ergot alkaloids synthesis (EAS) involves 12 genes expressed at the early (dmaW, easF, easC, easE), middle (easD, easA, easG) and late (easH, lpsA, lpsB, lpsC) stages in the biosynthetic pathway (cloA in both middle and late stages). Full DNA sequences of 11 EAS genes (excluding lpsA) were extracted from complete genomes of 30 strains belonging to six closely related Claviceps species. Comparison of DNA polymorphisms showed that divergence level (K) was apparently lower in the middle stages, especially easD and easA, resembling the hourglass model. This pattern was observed among six species and within C. purpurea and confirmed using a tree-based divergence analysis. We believe this is the first report of the hourglass model in a secondary metabolic pathway.
Investigating hybridization events between Ustilago maydis and Sporisorium reilianum. E. R. M STORFIE AND B. J. SAVILLE. (B.J.S.) Environmental and Life Sciences Graduate Program, Trent University, 2140 East Bank Drive, Peterborough, ON K9L 0G2, Canada; and (B.J.S., E.R.M.S.) Forensic Science Program, Trent University, 2140 East Bank Drive, Peterborough, ON K9L 0G2, Canada
To gain understanding of fungal hybridizations that could lead to emergent pathogens, we are investigating gene expression changes in Ustilago maydis × Sporisorium reilianum fusions. Both species infect maize; however, U. maydis produces localized infections, while S. reilianum infections are systemic. Isolates of these fungi fuse on plates, forming hybrid mycelial growth similar to that of U. maydis alone; but plants infected with hybrids show limited symptoms of infection. Analysis of preliminary RNA-seq data from the hybrid dikaryon relative to both mono-species dikaryons reveals a transcript population more similar to U. maydis than to S. reilianum. These analyses are being confirmed by optimizing fusion formation on plates and using reverse transcriptase PCR to assess RNA-seq-detected transcript level changes. Transcript levels are also being assessed during in planta hybrid growth to test the hypothesis that the limited signs of pathogenesis are the result of altered expression of U. maydis genes that are required for full pathogenesis. Select genes, with significantly altered transcript levels in the hybrid infections, will be over-expressed in either U. maydis or S. reilianum to determine if this expression influences the level of virulence by the hybrid. These investigations will provide information on transcript level patterns that correlate with the distinct infection modes of U. maydis or S. reilianum. They will also elucidate genes whose expression could influence the emergence of new pathogens or pathogenesis types. Towards this end, progress on investigations of transcript level changes in the hybrids relative to the mono-species dikaryons were presented.