β-D-XYLOSIDASE 4 modulates systemic immune signaling in Arabidopsis thaliana

Abstract

Pectin- and hemicellulose-associated structures of plant cell walls participate in defense responses against pathogens of different parasitic lifestyles. The resulting immune responses incorporate phytohormone signaling components associated with salicylic acid (SA) and jasmonic acid (JA). SA plays a pivotal role in systemic acquired resistance (SAR), a form of induced resistance that - after a local immune stimulus - confers long-lasting, systemic protection against a broad range of biotrophic invaders. β-D-XYLOSIDASE 4 (BXL4) protein accumulation is enhanced in the apoplast of plants undergoing SAR. Here, two independent Arabidopsis thaliana mutants of BXL4 displayed compromised systemic defenses, while local resistance responses to Pseudomonas syringae remained largely intact. Because both phloem-mediated and airborne systemic signaling were abrogated in the mutants, the data suggest that BXL4 is a central component in SAR signaling mechanisms. Exogenous xylose, a possible product of BXL4 enzymatic activity in plant cell walls, enhanced systemic defenses. However, GC-MS analysis of SAR-activated plants revealed BXL4-associated changes in the accumulation of certain amino acids and soluble sugars, but not xylose. In contrast, the data suggest a possible role of pectin-associated fucose as well as of the polyamine putrescine as regulatory components of SAR. This is the first evidence of a central role of cell wall metabolic changes in systemic immunity. Additionally, the data reveal a so far unrecognized complexity in the regulation of SAR, which might allow the design of (crop) plant protection measures including SAR-associated cell wall components.

Identification and Genetic Dissection of Resistance to Red Crown Rot Disease in a Diverse Soybean Germplasm Population

“…The expression level of the predicted genes Glyma.08G074600, Glyma.08G074700, and Glyma.12G043600 were appreciably upregulated in the resistant accession compared to the susceptible accession on the 7th day, which implies a possibility of its involvement in soybean's reaction to C. ilicicola resistance. For instance, the Glyma.08G074700 homolog in Arabidopsis, AT5G64570, encodes a secreted beta-d-xylosidase that enhances resistance to Botrytis cinerea [60] as well as boosts signaling related to systemic immunity in Arabidopsis thaliana [61].…”

The Relationship between the Sugar Preference of Bacterial Pathogens and Virulence on Plants

“…Furthermore, xylose has emerged as a prominently investigated sugar in plant disease contexts. Studies have showcased its potential to enhance the management of cucumber wilt disease ( Xu et al, 2019 ) and bolster colonization by the plant growth-promoting rhizobacterium B. velezensis , thereby mitigating wilt symptoms ( Bauer et al, 2023 ). Intriguingly, xylose was also found to have contrasting effects, serving both as a nutrient and a virulence enhancer for X. citri ( Alexandrino et al, 2023 ).…”

Low temperature, mechanical wound, and exogenous salicylic acid (SA) can stimulate the SA signaling molecule as well as its downstream pathway and the formation of fruiting bodies in Flammulina filiformis

“…SA as a hormone plays a critical role in the regulation of a multitude of physiological processes such as seed germination, vegetative growth, photosynthesis, respiration, thermogenesis, flower formation, seed production, responding to pathogens, and stimulating plant defense immunity (Lastochkina et al, 2020 ; Ansari et al, 2021 ). Under biotic stress conditions, SA fulfills a key function as an endogenous signal mediating local defense responses (Bauer et al, 2022 ; Zhang et al, 2023 ). In fungi, it has been found that high temperatures could increase the SA content in the extracellular fluid of Pleurotus ostreatus (Qiu et al, 2018 ).…”