Subcritical water extraction of Equisetum arvense biomass withdraws cell wall fractions that trigger plant immune responses and disease resistance

Abstract

Plant cell walls are complex structures mainly made up of carbohydrate and phenolic polymers. In addition to their structural roles, cell walls function as external barriers against pathogens and are also reservoirs of glycan structures that can be perceived by plant receptors, activating Pattern-Triggered Immunity (PTI). Since these PTI-active glycans are usually released upon plant cell wall degradation, they are classified as Damage Associated Molecular Patterns (DAMPs). Identification of DAMPs imply their extraction from plant cell walls by using multistep methodologies and hazardous chemicals. Subcritical water extraction (SWE) has been shown to be an environmentally sustainable alternative and a simplified methodology for the generation of glycan-enriched fractions from different cell wall sources, since it only involves the use of water. Starting from Equisetum arvense cell walls, we have explored two different SWE sequential extractions (isothermal at 160 ºC and using a ramp of temperature from 100 to 160 ºC) to obtain glycans-enriched fractions, and we have compared them with those generated with a standard chemical-based wall extraction. We obtained SWE fractions enriched in pectins that triggered PTI hallmarks in Arabidopsis thaliana such as calcium influxes, reactive oxygen species production, phosphorylation of mitogen activated protein kinases and overexpression of immune-related genes. Notably, application of selected SWE fractions to pepper plants enhanced their disease resistance against the fungal pathogen Sclerotinia sclerotiorum. These data support the potential of SWE technology in extracting PTI-active fractions from plant cell wall biomass containing DAMPs and the use of SWE fractions in sustainable crop production.

Linear β-1,2-glucans trigger immune hallmarks and disease resistance in plants

“…Despite these advances, it was even proposed that the slow progress in the study of glucantriggered immunity was due to the insensitivity of the Arabidopsis ecotype Col-0 to glucans (Fesel and Zuccaro, 2016). However, numerous studies published over the last decade have shown that Arabidopsis is a good system to study glucan-triggered immunity (Souza et al, 2017;Claverie et al, 2018;Johnson et al, 2018;Mélida et al, 2018;Locci et al, 2019;Wanke et al, 2020;Rebaque et al, 2021Rebaque et al, , 2023Zarattini et al, 2021;Tseng et al, 2022;Martín-Dacal et al, 2023). The studies of two research groups confirmed the data published by Aziz et al, (2007) a decade earlier on the ability of β-1,4-glucans to induce PTI responses in plants (Souza et al, 2017;Johnson et al, 2018).…”

“…Moreover, the emergence of immune priming using glycans from various sources has demonstrated efficacy in enhancing protection across different pathosystems, showcasing the potential of glycanbased technologies in plant defence (Klarzynski et al, 2000;Aziz et al, 2007;Gravino et al, 2015;Claverie et al, 2018;Rebaque et al, 2023). This concept has spurred the development of crop protection technologies focused on enhancing the natural resistance mechanisms of the plants to combat plant pathogens, promoting sustainable agricultural practices and reducing environmental impact (Conrath et al, 2015).…”