A review of knowledge on the mechanisms of action of the rare sugar <scp>d</scp> ‐tagatose against phytopathogenic oomycetes
Abdessalem Chahed, Andrea Nesler, Aziz Aziz, Essaïd Ait Barka, Ilaria Pertot, Michele Perazzolli
Abstract
Abstract d ‐tagatose is a rare monosaccharide, naturally present at low concentrations in some fruits and dairy products. d ‐tagatose is "generally recognized as safe" and is used as a low‐calorie sweetener in the food industry. I t is able to inhibit the growth of numerous microorganisms, such as phytopathogenic oomycetes responsible for important crop diseases. Thanks to the negligible effects on human health and the environment, d ‐tagatose has been proposed as a sustainable product for crop protection. This review describes the current knowledge on modes of action of d ‐tagatose against phytopathogenic oomycetes and its potential uses in agriculture. d ‐tagatose can negatively affect the growth of phytopathogenic oomycetes by inhibiting key enzymes of sugar metabolism, such as β‐glucosidase in Phytophthora infestans , and fructokinase and phosphomannose isomerase in Hyaloperonospora arabidopsidis . Moreover, d ‐tagatose affects sugar content, causes severe mitochondrial alterations, and inhibits respiration processes with the accumulation of reactive oxygen species in P . infestans , but not in P . cinnamomi . Differential effects of d ‐tagatose are associated with a global gene downregulation in P . infestans and with an efficient transcriptional reprogramming of multiple metabolic processes in P . cinnamomi . d ‐tagatose displays possible species‐specific effects in Phytophthora spp. and nutritional properties on some plant‐associated microorganisms. However, inhibitory effects are reversible and P . infestans growth can be restored in the absence of d ‐tagatose. Further functional studies are discussed in this review, in order to promote the use of d ‐tagatose for sustainable crop protection.