Fructans As DAMPs or MAMPs: Evolutionary Prospects, Cross-Tolerance, and Multistress Resistance Potential

Abstract

This perspective paper proposes that endogenous apoplastic fructans in fructan accumulating plants, released after stress-mediated cellular leakage, or increased by exogenous application, can act as damage-associated molecular patterns (DAMPs), priming plant innate immunity through ancient receptors and defense pathways that most probably evolved to react on microbial fructans acting as microbe-associated molecular patterns (MAMPs). The proposed model is placed in an evolutionary perspective. How this type of DAMP signaling may contribute to cross-tolerance and multistress resistance effects in plants is discussed. Besides apoplastic ATP, NAD and fructans, apoplastic polyamines, secondary metabolites, and melatonin may be considered potential players in DAMP-mediated stress signaling. It is proposed that mixtures of DAMP priming formulations hold great promise as natural and sustainable alternatives for toxic agrochemicals.

The fructan syndrome: Evolutionary aspects and common themes among plants and microbes

“…Zymomonas mobilis, G. diazotrophicus and Burkholderia pseudomallei have symbiotic relationships with Agave , sugarcane, and maize, respectively (Velázquez‐Hernández et al, ). In a recent perspective paper (Versluys, Tarkowski, & Van den Ende, ), the role of microbial fructans as microbe associated molecular patterns (MAMPs) in plant innate immunity has been discussed. In short, it was hypothesized that small hydrolytic products of microbial fructans may act as MAMPs and activate plant defense systems.…”

“…Being a small diffusible molecule, levanbiose was proposed by the authors to act as a signalling molecule that takes part in plant‐microbe communication. By extension, levan oligosaccharides produced by microbial endolevanases could be involved in plant–microbe (Versluys et al, ) or microbe–microbe communication as well. The possibility that small fructans can act as signals has also been raised in the plant context (Van den Ende, ; see also below).…”

Chicory R2R3-MYB transcription factors CiMYB5 and CiMYB3 regulate fructan 1-exohydrolase expression in response to abiotic stress and hormonal cues

“…It is noteworthy that FEH enzymes, termed defective invertases, are also found in non-fructan plants ( De Coninck et al , 2005 ; Le Roy et al , 2013 ), suggesting a possible role in the apoplast during plant defense against microbial pathogens. Recently, it has been hypothesized that in fructan accumulating plants, apoplastic fructans released after stress-mediated cell rupture can act as damage-associated molecular patterns (DAMPs) and microbe-associated molecular patterns (MAMPs), contributing to multi-stress resistance potential ( Versluys et al , 2017 ). Also, fructans could be delivered from the vacuole to extracellular space for protecting the plasma membrane by means of vesicle-mediated, tonoplast-derived exocytosis ( Valluru et al , 2008 ).…”

UDP-Glucose: A Potential Signaling Molecule in Plants?

“…There is no information on extracellular UDP-Glc in plants. Can the UDP-Glc released by dead cells potentially be perceived as a damage-associated molecular pattern (DAMP), similar to what is proposed for fructans ( Versluys et al, 2017 )? This might also explain the above-mentioned responses to exogenous application of UDP-Glc in plants.…”