Suppression of UV-B stress induced flavonoids by biotic stress: Is there reciprocal crosstalk?

Abstract

Plants respond to abiotic UV-B stress with enhanced expression of genes for flavonoid production, especially the key-enzyme chalcone synthase (CHS). Some flavonoids are antioxidative, antimicrobial and/or UV-B protective secondary metabolites. However, when plants are challenged with concomitant biotic stress (simulated e.g. by the bacterial peptide flg22, which induces MAMP triggered immunity, MTI), the production of flavonoids is strongly suppressed in both Arabidopsis thaliana cell cultures and plants. On the other hand, flg22 induces the production of defense related compounds, such as the phytoalexin scopoletin, as well as lignin, a structural barrier thought to restrict pathogen spread within the host tissue. Since all these metabolites require the precursor phenylalanine for their production, suppression of the flavonoid production appears to allow the plant to focus its secondary metabolism on the production of pathogen defense related compounds during MTI. Interestingly, several flavonoids have been reported to display anti-microbial activities. For example, the plant flavonoid phloretin targets the Pseudomonas syringae virulence factors flagella and type 3 secretion system. That is, suppression of flavonoid synthesis during MTI might have also negative side-effects on the pathogen defense. To clarify this issue, we deployed an Arabidopsis flavonoid mutant and obtained genetic evidence that flavonoids indeed contribute to ward off the virulent bacterial pathogen Pseudomonas syringae pv. tomato (Pst) DC3000. Finally, we show that UV-B attenuates expression of the flg22 receptor FLS2, indicating that there is negative and reciprocal interaction between this abiotic stress and the plant-pathogen defense responses.

Plant immunity in signal integration between biotic and abiotic stress responses

“…Under UV-B or excessive light stress, flavonoids are induced to provide sunscreens, antioxidants and/or antimicrobials (Schenke et al, 2019). MAMP signaling specifically suppresses UV-B-or sucrose-inducible flavonol biosynthesis in Arabidopsis (Saijo et al, 2009;Schenke et al, 2019), while it induces numerous defenserelated metabolites (e.g. phytoalexins, coumarin or lignin).…”

Root Skewing-Associated Genes Impact the Spaceflight Response of Arabidopsis thaliana

“…Considering that wounding and pathogen invasion also mechanically disrupt membranes and cell walls (Chen et al, 2016), these pathways may be signaling remodeling of cellular structures and the microtubule network in spaceflight. Flg22 application to Arabidopsis cell cultures and induction of MAMP-triggered immunity also has the effect of redistributing flavonoid compounds from biosynthetic processes important to oxidative stress response processes to the production of compounds important to defense (Schenke et al, 2019). Genes associated with the production of phenylpropanoids are less-represented among the spr1 DEGs downregulated in spaceflight compared to Col-0, although they are also more highly represented among spr1 DEGs downregulated across development in spaceflight (Figures 6B, 7B).…”

Burdock fructooligosaccharides inhibits postharvest colour development in grape skins by altering phenylpropanoid fluxes from anthocyanin to the resistance‐related phenolic substances

“…In Salvia miltiorrhiza , the silencing of the CHS gene enhanced the concentration of the resistance‐related phenolic substances and decreased the concentration of flavonoids (Schenke et al ). The changes from flavonoid synthesis to stilbenes via CHS downregulation and STS upregulation were observed in grape cell culture in response to fungal elicitors (Mutawila et al ).…”

“…In Arabidopsis , MYB4 acted as a critical regulator to alter the fluxes of intermediate products into the anthocyanin or lignin pathways. The upregulation of MYB4 slowed the biosynthesis of anthocyanin, whereas it induced the biosynthesis of lignin (Allan and Espley , Schenke et al ). Therefore, this study indicated that MYB4 plays a critical role in regulating the functional genes CHS , CCR and CAD , and as a result, inhibits the biosynthesis of anthocyanin.…”