Accumulation of Isochorismate-derived 2,3-Dihydroxybenzoic 3-O-β-d-Xyloside in Arabidopsis Resistance to Pathogens and Ageing of Leaves

Abstract

An intricate network of hormone signals regulates plant development and responses to biotic and abiotic stress. Salicylic acid (SA), derived from the shikimate/isochorismate pathway, is a key hormone in resistance to biotrophic pathogens. Several SA derivatives and associated modifying enzymes have been identified and implicated in the storage and channeling of benzoic acid intermediates or as bioactive molecules. However, the range and modes of action of SA-related metabolites remain elusive. In Arabidopsis, Enhanced Disease Susceptibility 1 (EDS1) promotes SA-dependent and SAindependent responses in resistance against pathogens. Here, we used metabolite profiling of Arabidopsis wild type and eds1 mutant leaf extracts to identify molecules, other than SA, whose accumulation requires EDS1 signaling. Nuclear magnetic resonance and mass spectrometry of isolated and purified compounds revealed 2,3-dihydroxybenzoic acid (2,3-DHBA) as an isochorismate-derived secondary metabolite whose accumulation depends on EDS1 in resistance responses and during ageing of plants. 2,3-DHBA exists predominantly as a xylose-conjugated form (2-hydroxy-3-␤-O-D-xylopyranosyloxy benzoic acid) that is structurally distinct from known SA-glucose conjugates. Analysis of DHBA accumulation profiles in various Arabidopsis mutants suggests an enzymatic route to 2,3-DHBA synthesis that is under the control of EDS1. We propose that components of the EDS1 pathway direct the generation or stabilization of 2,3-DHBA, which as a potentially bioactive molecule is sequestered as a xylose conjugate.

Exploiting Natural Variation of Secondary Metabolism Identifies a Gene Controlling the Glycosylation Diversity of Dihydroxybenzoic Acids in Arabidopsis thaliana

“…This analysis confirmed that they are DHBA glycosides and revealed that the sugar moiety is b-D-xylose in both compounds 3 and 4. The 1 H and 13 C NMR spectra of compounds 3 and 4 agreed with those previously described for 2,5-DHBA 5-O-b-D-xyloside (2,5-DHBAX) and 2,3-DHBA 3-O-b-D-xyloside (2,3-DHBAX), respectively ( Figure 3C; Table S1) (Fayos et al 2006;Bartsch et al 2010). We reexamined Col-0 by more sensitive methods and were able to detect 2,5-DHBAX using fluorescence detection or LC-MS, although the level of this compound was below the detection limit of the UV detector used in our initial HPLC profiling experiments (data not shown).…”

“…Feeding experiments using isotope-labeled SA demonstrated that 2,5-DHBA and 2,3-DHBA could be made from SA in leaves of various plants including Arabidopsis (Ibrahim and Towers 1959;Bartsch et al 2010). Consistent with this observation, Arabidopsis isochorismate synthase mutant sid2, which is defective in SA biosynthesis, was found to be deficient in DHBA glycosides (Bartsch et al 2010).…”

“…DHBA glycoside biosynthesis has been implicated in defense responses and leaf senescence regulation (Belles et al 1999;Fayos et al 2006;Bartsch et al 2010;Zhang et al 2013), but it is yet unclear whether these are due to modulation of SA activity or new activities conferred by DHBAs and/or their glycosides. Glycosylation is a common modification that contributes to the diversity of secondary metabolism.…”

Discovering variation of secondary metabolite diversity and its relationship with disease resistance inCornus floridaL.

“…Other SNP loci like B440 may encode regulatory proteins (Fan et al., 2016; Sawaki et al., 2009), which similarly respond to stress by regulating transcription of genes involved in pathways such as immunity response. Biomarker M435T576 and its related metabolites belong to a class of terpenoid derivatives that have known antimicrobial and antifungal properties (Bartsch et al., 2010; Chang, Xuan, Xu, & Zhang, 2001; Meng, Lu, Li, Yang, & Tan, 1999; Whitehead, Tiramani, & Bowers, 2016) and are likely sensitive to disease‐mediated signaling processes (Caplan, Padmanabhan, & Dinesh‐Kumar, 2008). For instance, M227T630 was identified as Cornolactone C, an iridoid isolated previously from C. florida (He et al., 2014), which belongs to a compound class known to accumulate in response to infection and has documented antimicrobial properties (Marak, Biere, & Van Damme, 2002).…”

The Vascular Pathogen Verticillium longisporum Requires a Jasmonic Acid-Independent COI1 Function in Roots to Elicit Disease Symptoms in Arabidopsis Shoots

“…S3). SAG might serve as a storage form of SA, whereas DHBA, which has a weak PR-1-inducing activity (Bartsch et al, 2010), is likely to be the activemetabolite. Expression of PR-1 was partially reduced in dde2-2 and even further compromised in coi1-t (Fig.…”