Fructans Prime ROS Dynamics and Botrytis cinerea Resistance in Arabidopsis

Abstract

Naturally derived molecules can be used as priming or defense stimulatory agents to protect against biotic stress. Fructans have gained strong interest due to their ability to induce resistance in a number of crop species. In this study, we set out to establish the role of fructan-induced immunity against the fungal pathogen Botrytis cinerea in Arabidopsis thaliana. We show that both inulin- and levan-type fructans from different sources can enhance Arabidopsis resistance against B. cinerea. We found that inulin from chicory roots and levan oligosaccharides from the exopolysaccharide-producing bacterium Halomonas smyrnensis primed the NADPH-oxidase-mediated reactive oxygen species (ROS) burst in response to the elicitors flg22, derived from the bacterial flagellum, and oligogalacturonides (OGs), derived from the host cell wall. Neither induced a direct ROS burst typical of elicitors. We also found a primed response after infection with B. cinerea for H2O2 accumulation and the activities of ascorbate peroxidase and catalase. Sucrose accumulated as a consequence of fructan priming, and glucose and sucrose levels increased in fructan-treated plants after infection with B. cinerea. This study shows that levan-type fructans, specifically from bacterial origin, can prime plant defenses and that both inulin and levan oligosaccharide-mediated priming is associated with changes in ROS dynamics and sugar metabolism. Establishing fructan-induced immunity in Arabidopsis is an important step to further study the underlying mechanisms since a broad range of biological resources are available for Arabidopsis.

Spermine and Spermidine Priming against Botrytis cinerea Modulates ROS Dynamics and Metabolism in Arabidopsis

“…For all experiments, B. cinerea strain B05.10 obtained from Prof. Dr. Barbara De Coninck (KU Leuven, Division of Crop Biotechnics, Leuven, Belgium) were used [ 39 , 40 ]. To generate spores, we grew B. cinerea on 24 g/L potato dextrose agar (PDA) for 14 days at 21 °C in the dark.…”

“…Soluble sugars were extracted and quantified as previously explained [ 40 ]. Frozen leaf material was grinded in liquid nitrogen using a mortar and pestle, and 100 mg extracted in 1 mL ddH 2 O by boiling for 15 min at 95 °C.…”

“…Spores were incubated at room temperature for 4 h prior to infection to allow for synchronous germination. Infections were conducted as described previously [40]. Three source leaves per plant (rosette leaves 5-7) were cut, rinsed in ddH 2 O, and blotted with paper towel to remove residual priming compounds from the leaves.…”

“…Soluble sugars were extracted and quantified as previously explained [40]. Frozen leaf material was grinded in liquid nitrogen using a mortar and pestle, and 100 mg extracted in 1 mL ddH 2 O by boiling for 15 min at 95 • C. Samples were vortexed and centrifuged for 10 min at 15,000× g to remove plant debris and supernatant was desalted by applying 200 µL to a Dowex anion and cation exchange column prepared in glass Pasteur pipettes.…”

Functional and Molecular Characterization of the Halomicrobium sp. IBSBa Inulosucrase

“…While many 3D structures of levansucrases are available, so far only one structure is available for inulosucrase [ 34 ]. All these enzymes and/or fructans produced from their respective source organisms are particularly interesting in terms of industrial applications, including their use as prebiotics, immunomodulators, priming compounds as well as for an array of food and nonfood applications [ 35 , 36 , 37 , 38 , 39 ]. Fructan-producing lactic acid bacteria gained great attention in the fermented food sector, contributing to the increased production of healthy foods [ 40 ].…”