The rare sugar D-tagatose protects plants from downy mildews and is a safe fungicidal agrochemical
Susumu Mochizuki,Takeshi Fukumoto,Toshiaki Ohara,Kouhei Ohtani,Akihide Yoshihara,Yoshio Shigematsu,Keiji Tanaka,Koichi Ebihara,Shigeyuki Tajima,Kenji Gomi,Kazuya Ichimura,Ken Izumori,Kazuya Akimitsu,et al.
COMMUNICATIONS BIOLOGY|(2020)3:423|https://doi.org/10.1038/s42003-020-01133-7|www.nature.com/commsbioAbstract
The rare sugar D-tagatose is a safe natural product used as a commercial food ingredient.Here, we show that D-tagatose controls a wide range of plant diseases and focus on downy mildews to analyze its mode of action. It likely acts directly on the pathogen, rather than as a plant defense activator. Synthesis of mannan and related products of D-mannose metabolism are essential for development of fungi and oomycetes; D-tagatose inhibits the first step of mannose metabolism, the phosphorylation of D-fructose to D-fructose 6-phosphate by fructokinase, and also produces D-tagatose 6-phosphate. D-Tagatose 6-phosphate sequentially inhibits phosphomannose isomerase, causing a reduction in D-glucose 6-phosphate and D-fructose 6-phosphate, common substrates for glycolysis, and in D-mannose 6-phosphate,needed to synthesize mannan and related products. These chain-inhibitory effects on metabolic steps are significant enough to block initial infection and structural development needed for reproduction such as conidiophore and conidiospore formation of downy mildew.