Characterization of trichothecene hydroxylation enzymes and screening of trichothecene production inhibitors were performed to decrease the frequency of false detection and reduce grain contamination by trichothecene mycotoxins. Molecular genetic studies of trichothecene biosynthetic genes revealed that the trichothecene C-4 hydroxylase, FgTRI13p, encoded by FgTri13 of Fusarium graminearum, has co-evolved with the C-7/C-8 hydroxylase, FgTRI1p, encoded by FgTri1. FgTRI13p shows highly restricted substrate specificity for trichothecene intermediates compared with FsTRI13p produced by Fusarium sporotrichioides. A glutamine analog, acivicin, was screened as an inhibitor of trichothecene production from the chemical library of the RIKEN Natural Products Depository. The predicted mode of action of acivicin in F. graminearum was that the acivicin-induced nutrient starvation repressed the trichothecene master regulator encoded by FgTri6, which blocked trichothecene production. In addition, another trichothecene production inhibitor NPD352 [testosterone 3-(O-carboxymethyl)oxime amide-bonded to phenylalanine methyl ester] was obtained from the library by chemical array screening using trichodiene synthase (FgTRI5p) as a target protein. The mixed-type inhibitor NPD352 may bind and interfere with intracellular FgTRI5p under conditions favoring trichothecene production.
Recent advances in genome determination provided an insight that filamentous fungi have many and much varied genes involved in secondary metabolism. Most of them remain unstudied, which provides room for investigation of potential drug lead compounds. We studied secondary metabolism in filamentous fungi by using transcriptome data and comparing newly obtained genome sequences among closely related species. These works resulted in discovery of a gene cluster involved in biosynthesis of conidia-specific accumulated compound trypacidin, and shed light on complex evolution of secondary metabolism in filamentous fungi.
Fusarium fujikuroi is the fungal pathogen of rice bakanae disease. This fungus is known to produce secondary metabolites including gibberellin that function as a plant hormone and fumonisin as a mycotoxin. Two groups were discovered in F. fujikuroi derived from not only diseased rice plant but also from various resources by phylogenetic analyses and investigation of gibberellin and fumonisin producibility. In this proceeding, gibberellin production difference between these groups and its contributory factor in F. fujikuroi were presented.
Crops used for current agriculture have been largely modified from the original plants by various breeding techniques. Crossing between plants with good traits allows to generate a plant with desired characteristics. Mutants with desired properties are also established by choosing from the plants treated by radiation or chemicals as mutagen. Recently, crops possessing new traits have been developed using recombinant DNA technologies, and they are widely distributed in the world. Genome editing technique was developed around 2010. A tool for genome editing, such as CRISPR/Cas9 consisting of an artificial nuclease that recognizes specific sequences, induces a desired mutation into a specific gene. We developed a novel genome-editing system using dMac3, a translation enhancer, and optimized for plants. This increases the efficiency of the targeted mutagenesis. We produced a CRISPR/Cas9 gene that targeted the granule-bound starch synthase gene (GBSS) involved in the production of amylose in the starch of the tubers. Using this, we created potato GBSS mutants in which four alleles of potato tetraploid genome contained mutant genes, resulting in a property of low amylose trait in their tuber starch.
International Conference of Mycotoxicology (ICM 2018) was held from Feb 14 th to 15 th, 2018, at Kasetsart University, Bangkok, Thailand. The conference theme was “Driving Mycotoxin Research Toward Global Food Security”. Approximately 230 people participated to this conference, and 18 lectures and 13 scientific posters were presented throughout the program. The author was invited by Dr. Amnart Poapolathep, the organizer, to deliver the lecture ‘Analysis of Fusarium mycotoxins by liquid chromatography-mass spectrometry (LC-MS)’. This report briefly shows the contents of this conferences.
Last February, I had an opportunity to visit Regional Mycotoxin Laboratory where equips an Aflasafe modular plant in Kenya Agricultural & Livestock Research Organization (KALRO) Katumani Research Centre, Machakos, Kenya, thanks to Ms. Annette Nyangaresi’s thoughtful arrangement and Dr. Mutegi Charity’s kind coordination. I accompanied with Ms. Annette Nyangaresi, her supervisor Prof. Yoshiharu Fujii (Tokyo University of Agriculture and Technology), and Prof. Willis Owino (Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya). Here I would like to introduce the outline of this facility.